Thank you to all who helped out with the tinting advice.
Here's a quick recipe that I've mixed...and it works (woo hoo!).
8 parts (Elmers) white glue to 1 part (Crayola) tempera. (I'm being specific about the brands because someone said that certain brands wil NOT mix...fortunately I don't know which ones those are)
The end product makes a fantastic textured outliner - it is a bit brittle, but it works great on paper. It doesn't stick on slick surfaces (plastic, glass, coated paper, etc.) - which may work out great for a different sort of assignment...perhaps making textural shapes to use on a later project (???)
The marker nibs are a fantastic idea - when I have time I'm going to experiment with that too.