[QUESTIONS and ANSWERS] Walkthroughs for the Heroes 3: RoE, AB, and SoD campaigns.

Hello. Briefly about what happened: I installed Heroes 3, played a bit myself, and after a while, I wanted to play with a friend on the same computer. I thought it wouldn't be a problem, but...
Question: is it possible to play as allies? (specifically, with the color I want).
If so, please tell me how?