They are just the Win & Mac system color picker,
you can use the eye dropper to pick the colors from the Windows picker image and add them to the Mac's pallet.
You have the RGB sliders that you can enter the RGB value.

Attached Files (Click to download or enlarge) (Only available when you are logged in)
Reaper-Win-Mac-System-Color-Picker.png (227.35 KB, 46 downloads)
Reaper-Win-Mac-System-Color-Picker2.png (184.87 KB, 40 downloads)