Studies show that food tastes better around red, so plant red flowers around outdoor eating areas to help stimulate conversation and make food taste better. Masses of red, yellow or orange annual flowers are guaranteed attention getters. You can find true reds in varieties of salvia, celosia, zinnia, geranium, and wax begonia. Marigolds and zinnias are often used for yellows and oranges, but for something different try dwarf sunflowers, calendula, gazania, gaillardia or nasturtiums. If red and yellow excite and draw attention, then blue is the color we perceive as being cool and calm.
Lighter blues are better than dark blues.
Those 95-degree days will feel cooler in a garden with blue flowers. Blue tones can help widen or lengthen the look of a garden because blue falls back visually. Lots of blue flowers planted along the sides of a long, narrow garden will make it seem wider. Because blue is the first color to fade from sight as night falls, you may want to incorporate light colors into a blue border if you use your garden more in the evening. Blue tones in annuals are found in petunias, blue salvia, lisianthus, ageratum and lobelia.