GG,

Better Homes and Garden has a free garden design tool. There is also some relatively inexpensive software that will let you pre-visualize various garden layout options.

ZM
(not associated with any product or vendor mentioned or linked)

It's really quite simple. Draw your bed to scale on graph paper. Then draw lines through the beds until you get a pattern that you like. Count the squares on your graph to figure out how many plants of each color you want, and then next year, transfer the lines onto your bed. You can "draw" the lines on the dirt with flour, or you can stretch out string between stakes to make straight lines. Then just fill in the plants inside the lines.

One simple to do idea would be to center a triangle in the bed and fill it with one color. Then plant another color outside the triangle to the edge of the bed on either side.

This works best with plants that make uniform mounds or that can be clipped. Impatiens should work very well. I have done this kind of planting in my fall and winter garden with kale, collards, and mustard greens. It's really just a variation of making a knot garden.

Thanks for the info. What is a knot garden?

A knot garden is an intricate design made by using plants of various types to make patterns in color, shape, and/or texture.

Here is a link that might be useful: Google Image Search for Knot Gardens