What is plaster of paris?

What is the best solution to selectively paint or tint plaster of paris?

• I'm looking to tint merely a portion of a plaster of paris cast (i.e. a paw print within in a cast). I still want the detail of the skin in the print, and want to leave the remainder of the cast white. I know Plaster is absorbent, so all I want is the tint. I'm thinking pastel colors, just to make it pop a little more against the white. Watercolor? Watered down acrylic? Should the entire thing be sealed once I achieve the color I want? Again, I want intricate details to remain intact.

• Answer:

  Water color. Practice on some extra pieces or on the bottom to see how light it ends up as it soaks in.