ADD Planner lets you customize the color scheme. Here's how you do it:
And here's a before and after of how ADD Planner looks with the new colors:
Notice that the program colors do not affect tasks which have a category or custom color defined on the Category/Color tab on the Add/Edit Task dialog.
If you don't like the new color scheme, you can go back to the Color Options dialog and click the "Reset Colors" button to restore the default color scheme.