The colorant I've been playing with is a product called 'paint'. I was doing some reading and I came across an article about coloring plaster. Latex paint was suggested. The process is quite simple.

1) measure out your water.
2) Add some paint and mix thoroughly. I'm adding some black in my tests.
3) Add your plaster. Take into account the added weight of the paint in your mix.

Adding just a little bit of black is giving my bricks a nice gray color, much like light gray Merlins Magic. I'll be playing around with other other colors of paint after I finish the walls of Andaville.

Naloomi