!set [dcolor or was it dcolour?] [element] [number]
Both dcolour and dcolor will work. Use a hexadecimal colour (0xAARRGGBB - alpha, red, green, blue) for [number].
For example: !set dcolour dust 0xFFFFA0C0 will make all dust pink.
Edit:
More examples:
0xFFFF0000 - red
0xFF00FF00 - green
0xFF0000FF - blue
If you go into "pick colour" in the deco editor, it will tell you the hexadecimal for a colour.
You can get the codes for elements in the decoration menu, where you paint elements, if you click the small square that has the selected color a window appears and has hexadecimal code for the selected color.
I use colorpicker.com