read below code carefully, and do changes without hampering the original theme and features as i suggest later .

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Sticky Notes</title>
    <style>
        body {
            font-family: Arial, sans-serif;
            background-color: #f9f9f9;
            margin: 0;
            padding: 0;
        }

        .notes-container {
            display: flex;
            flex-wrap: wrap;
            justify-content: center;
            margin: auto;
            padding: 20px;
            width: 100%;
        }

        .note {
            margin: 20px;
            padding: 60px 20px 20px 20px;
            border-radius: 5px 5px 5px 20px; /* folder-like shape */
            box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
            width: 240px;
            position: relative;
            overflow: hidden;
            background-color: #FFFFD1; /* pastel yellow default color */
            min-height: 150px;
            height: auto;
        }

        .note textarea {
            width: 100%;
            height: calc(100% - 70px); /* Adjusts to fill available space minus padding */
            resize: none;
            border: none;
            background: transparent;
            font-family: inherit;
            outline: none;
            display: block;
        }

        .toolbar {
            position: absolute;
            top: 10px;
            left: 10px;
            display: flex;
            gap: 10px;
        }

        .toolbar button, .toolbar img {
            width: 20px;
            height: 20px;
            cursor: pointer;
            background: none;
            border: none;
            color: #555;
            filter: invert(40%); /* gray tint to match font */
        }

        .add-note-btn, .export-import button {
            margin: 5px;
            padding: 10px 20px;
            font-size: 16px;
            border: none;
            border-radius: 5px;
            cursor: pointer;
            background-color: #4CAF50;
            color: white;
        }

        .date-time {
            position: absolute;
            top: 10px;
            right: 10px;
            font-size: 0.8em;
            color: #555;
        }

        .export-import {
            position: fixed;
            top: 20px;
            left: 20px;
            display: flex;
            flex-direction: column;
            gap: 10px;
        }

        .color-picker-container {
            display: flex;
            gap: 5px;
            margin-left: 20px;
            margin-top: 20px;
        }

        .color-choice {
            width: 20px;
            height: 20px;
            border-radius: 50%;
            cursor: pointer;
            box-shadow: 0 1px 3px rgba(0, 0, 0, 0.2);
        }
    </style>
</head>
<body>

    <div class="export-import">
        <button class="add-note-btn" onclick="addNote()">Add Note</button>
        <div class="color-picker-container" id="color-picker-container">
            <!-- Pastel color choices -->
            <div class="color-choice" style="background-color: #FFDDC1;" onclick="selectColor('#FFDDC1')"></div>
            <div class="color-choice" style="background-color: #FFCCD2;" onclick="selectColor('#FFCCD2')"></div>
            <div class="color-choice" style="background-color: #D5AAFF;" onclick="selectColor('#D5AAFF')"></div>
            <div class="color-choice" style="background-color: #C1E1FF;" onclick="selectColor('#C1E1FF')"></div>
            <div class="color-choice" style="background-color: #C1FFC1;" onclick="selectColor('#C1FFC1')"></div>
            <div class="color-choice" style="background-color: #FFFFD1;" onclick="selectColor('#FFFFD1')"></div>
            <div class="color-choice" style="background-color: #D1FFF2;" onclick="selectColor('#D1FFF2')"></div>
        </div>
        <button onclick="exportNotes()">Export</button>
        <input type="file" id="importFile" onchange="importNotes()" style="display: none;">
        <button onclick="document.getElementById('importFile').click()">Import</button>
    </div>

    <div id="notes-container" class="notes-container"></div>

    <script>
        let selectedColor = '#FFFFD1'; // pastel yellow default color

        function addNote() {
            const noteContainer = document.getElementById('notes-container');
            const note = document.createElement('div');
            note.className = 'note';
            note.style.backgroundColor = selectedColor;

            const toolbar = document.createElement('div');
            toolbar.className = 'toolbar';
            toolbar.innerHTML = `
                <button onclick="document.execCommand('bold', false, '')">
                    <img src="https://img.icons8.com/ios-filled/50/000000/bold.png" alt="Bold" title="Bold">
                </button>
                <button onclick="document.execCommand('italic', false, '')">
                    <img src="https://img.icons8.com/ios-filled/50/000000/italic.png" alt="Italic" title="Italic">
                </button>
                <button onclick="document.execCommand('underline', false, '')">
                    <img src="https://img.icons8.com/ios-filled/50/000000/underline.png" alt="Underline" title="Underline">
                </button>
                <button onclick="deleteNote(this)">
                    <img src="https://img.icons8.com/ios-filled/50/000000/trash.png" alt="Delete" title="Delete">
                </button>
            `;
            note.appendChild(toolbar);

            const textarea = document.createElement('textarea');
            textarea.placeholder = 'Enter your note here...';
            textarea.oninput = function () {
                this.style.height = 'auto';
                this.style.height = this.scrollHeight + 'px';
            };
            note.appendChild(textarea);

            const dateTime = document.createElement('div');
            dateTime.className = 'date-time';
            const now = new Date();
            const formattedDate = now.toLocaleDateString('en-GB', {
                day: '2-digit',
                month: '2-digit',
                year: 'numeric'
            });
            const formattedTime = now.toLocaleTimeString('en-GB', {
                hour: '2-digit',
                minute: '2-digit',
                hour12: true
            });
            dateTime.textContent = `${formattedDate} ${formattedTime}`;
            note.appendChild(dateTime);

            noteContainer.appendChild(note);
        }

        function selectColor(color) {
            selectedColor = color || '#FFFFD1'; // default to pastel yellow
        }

        function deleteNote(button) {
            const note = button.closest('.note');
            note.remove();
        }

        function exportNotes() {
            let notesData = '';
            const notes = document.querySelectorAll('.note textarea');
            notes.forEach(note => {
                notesData += note.value + '\n\n---\n\n';
            });

            const blob = new Blob([notesData], { type: 'text/plain' });
            const a = document.createElement('a');
            a.href = URL.createObjectURL(blob);
            a.download = 'notes.txt';
            a.click();
        }

        function importNotes() {
            const fileInput = document.getElementById('importFile');
            const file = fileInput.files[0];

            if (file) {
                const reader = new FileReader();
                reader.onload = function (e) {
                    const content = e.target.result;
                    const notesData = content.split('\n\n---\n\n');

                    notesData.forEach(text => {
                        if (text.trim()) {
                            const noteContainer = document.getElementById('notes-container');
                            const note = document.createElement('div');
                            note.className = 'note';
                            note.style.backgroundColor = selectedColor;

                            const toolbar = document.createElement('div');
                            toolbar.className = 'toolbar';
                            toolbar.innerHTML = `
                                <button onclick="document.execCommand('bold', false, '')">
                                    <img src="https://img.icons8.com/ios-filled/50/000000/bold.png" alt="Bold" title="Bold">
                                </button>
                                <button onclick="document.execCommand('italic', false, '')">
                                    <img src="https://img.icons8.com/ios-filled/50/000000/italic.png" alt="Italic" title="Italic">
                                </button>
                                <button onclick="document.execCommand('underline', false, '')">
                                    <img src="https://img.icons8.com/ios-filled/50/000000/underline.png" alt="Underline" title="Underline">
                                </button>
                                <button onclick="deleteNote(this)">
                                    <img src="https://img.icons8.com/ios-filled/50/000000/trash.png" alt="Delete" title="Delete">
                                </button>
                            `;
                            note.appendChild(toolbar);

                            const textarea = document.createElement('textarea');
                            textarea.value = text.trim();
                            note.appendChild(textarea);

                            const dateTime = document.createElement('div');
                            dateTime.className = 'date-time';
                            const now = new Date();
                            const formattedDate = now.toLocaleDateString('en-GB', {
                                day: '2-digit',
                                month: '2-digit',
                                year: 'numeric'
                            });
                            const formattedTime = now.toLocaleTimeString('en-GB', {
                                hour: '2-digit',
                                minute: '2-digit',
                                hour12: true
                            });
                            dateTime.textContent = `${formattedDate} ${formattedTime}`;
                            note.appendChild(dateTime);

                            noteContainer.appendChild(note);
                        }
                    });
                };
                reader.readAsText(file);
            }
        }
    </script>
</body>
</html>