Ah, so I eventually found the scripting guide and learned that I could add this line at the beginning:
Code:
SetColourRGB(ColourR(), ColourG(), ColourB());
And that will set the color used in the script to be the color already selected.
There's also a SetToolProperty() function that looks like it might let you retain other settings as selected by the user, but I'm not clear on how it works. The color was the main thing I was interested in anyway, so I'm good for now.
Would still love it if there were a way to prompt for the color in the middle of a script.
-Tandava