Don’t think of it as difficult, think of it as adventurous! Plus we are going to make it easier for you.
Pick out a large pattern that contains “your” three colors. Then a medium-sized pattern (stripes work great for this) that contains one or two of those colors, then a small subtle pattern also with one or two of the colors. Here are a few pattern mixes to try:
floral pattern, geometric pattern, solid color
checkered pattern, ticking stripe, twill
animal pattern, basket weave, damask
A variation is to use a busy pattern, a simple pattern and a solid color. The busy pattern should be the largest pillow or the one that is front and center, since it will dictate the tone of the arrangement. Plaids and stripes work well as simple patterns.
Each pattern needs to stand out from the others. Too many like patterns compete with each other and cancel each other out. Your eyes do not know where to look. A large pattern, medium and small make an attractive and balanced arrangement.