Warm colors are red, yellow, and orange. Cool colors are blue, purple, and green. I use a little white with any combination. Basic garden design mandates taller plants in the back of a rectangular bed, or in the center, if it's a circular bed. Short plants are put in the front for the border, and medium height plants go in between.
Color needs to be spread throughout the garden.
Don't restrict yellow to the back, red to the middle, and white to the front. Each height needs each color that you have chosen. Say you choose a cool color scheme - blue, purple, green, and white. A blue morning glory could even climb above the garden. Green coleus is an effective mid-height foliage plant.