The use of color in the garden is a powerful tool -when used correctly. Here are some links to sites and articles that discuss landscape color:
Using color to set the mood in landscaping
Video about using a color wheel -gives you a little bit of an understanding about how colors are percieved.
The Impact of Color on Learning
This article highlights research on colors effect on learning and psychology in a school setting
Virtual color wheel that you can use on your Android tablet. Just match the color of the flowers you are considering using with this application and jot down the RGB code for that color. Later on you can use Photoshop or paint and 'paint in' the color scheme over a photograph of your garden using the codes.
Another interactive color wheel.
Proven Winners: Select from the 100's of 'Proven Winner' color annuals, biennials and perennials by color: