Herculiner can be painted though, it is best to use a polyurethane based paint to coat the surface with. Colored polyurethanes may be a little harder to find, but because they are like material and have the same pliability, you will get the longest lasting coverage with it. The usage of polyurethane paint is recommended because other types of paint will not have the same pliability and will be more apt to crack and peel off at a much quicker rate. You can use any other paint if you'd like, except for lacquer, but it may not hold up as long as the polyurethane.
If you can, the best time to apply the paint is within 24 hours of the Herculiner becoming dry to the touch. It will be in it's most receptive state for paint at that time. So after you apply the final coat of Herculiner, give it the recommended one to four hour time frame to set or wait until the surface isn't tacky anymore, then put the paint on. If you go a prolonged amount of time between applying the product and painting, we usually recommend lightly sanding and cleaning the surface of the Herculiner before applying.
What you don't want to do is mix anything into the Herculiner before applying it, even if it is a urethane product. There is a specific amount of plasticizer for curing that is in the product that will be affected if anything additional is added and there is the chance that the tint would not be compatible with the polyurethane we use in our product. Even mixing one Herculiner color with another can cause curing issues because certain colors use different types of polyurethane as well.