You might test a procion dye. I haven't tried these yet, but I am gearing up to do so. They are specifically made for organic products such as paper, fabric and wood. Like I said, I haven't given them a go yet, so I don't know if there will be a problem with epoxy adhering correctly. I suspect as long as it isn't oily and doesn't plug the wood grain, they should be ok, but only a test will tell.

Coloring individual strips before placing them would be difficult. They will be planed and sanded afterwards. Most dyes I've seen do not penetrate the wood very far unless it has been applied under pressure.

Bill