For the Brazilian keratin treatment, I know they say you have to wait at least two weeks to color hair after getting it done. How important is the wait time?

Very important! The issue is that the keratin treatment works because it closes tight the cuticle layer of your hair. Therefore, color will be difficult to take and might not take at all. The 2 weeks allows for the cuticle layer to soften a bit, allowing optimal penetration of the color through your hair shaft. Salon AKS