SpaceMan made me do it! Spaceman is making some neat stuff and sharing a lot of great ideas and tutorial sorts of stuff in his thread. Spaceman, you are a peach of a person!
One of the things he put up is a bunch of color swatches and samples (Scroll down, there are a bunch) and some discussion on how to get them into ZBrush in some useful way. I got lucky and tried to do something over my head with SpotLight which did not work due to some ugly artifacts and stuff, but I did come up with something FAR better as a result and its very easy to do. I'm going to copy what I put in his thread to here cause I think its seriously useful.
Here is the workflow:
Dock your Texture Menu ((this makes life easier) the one from the top, not the one on the left)).
Import the swatch image(s) you want to use.
Click once on the icon for that image in the Texture Menu.
Click the Add To SpotLight Button.
Hit the letter Z on your keyboard to turn on SpotLight, your image should now be visible.
In the ColorPicker down on the left side of the ZBrush window, Click, Hold and Drag out onto the color you want in the Swatch image being displayed by SpotLight.
Hit Shift and the Z key to get out of SpotLight, hide the swatch image, and begin painting and/or sculpting.
Yell Eureka!
Spotlight allows you to load a LOT of images into it so you could load in a couple of dozen of these color pallet thingys and pop them up in a split second when ever you needed to.