(a low priority wish): It would be nice to be able to set category colors from within Twinkle (rather than TwinkEdit), the reason being that the colors often look different on Palm.
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You can set colors inside Twinkle. Perhaps I don't have the feature documented well enough. From inside the "Edit Categories" form, select the box showing the color you wish to change. A new dialog showing all of the palm colors will pop up.