real color picker

[joshmarinacci]

The color property sheet should optionally use the native color picker

[blairmacintyre]

@joshmarinacci this is slighty more urgent, in that kids want to change the color on things, and the opacity. So, may want to bump this up (or, perhaps, at least add "R G B A" entry fields as a simple first step, with a preview of the color in the leftmost box in the set)

[blairmacintyre]

As I said here, at least put the three R/G/B fields (with a preview) below the line of color buttons, and then have the color buttons fill in the appropriate values, and use them; then people can just change the color values directly if they want

[joshmarinacci]

I've started on this. You now get a popup with the color buttons and a field to type in a hex value.