They are a completely different chemistry. You might be able to use the Alumilite dyes in PR, but I don't think mixing Alumilite, and PR is going to accomplish anything positive. What effect are you trying to achieve? There may be an easy way to do it.
Well, I don't have the answer to your question but, I would be very interested to know what the result would be. Infact, I very curious about the possibility that something very strange and workable, could come out as a result.
I'm trying to think if the 2 resin types would separate after mixed and before setting, both resin have a different curing time and process but, I don't think that, they would separate, maybe become clumpy and that would be a magnificent way to create blanks that would be possibly different than anything you know.
I may order a small 1lt tin of Polyurethane resin from my resin supplier, as I only use Polyester and try it myself, if no one here is willing to do it...! I betcha that, a few blokes will rush to try it themselves, just in case if turns out a great idea and claim that, was their idea. I will be watching this closely now that I stirred the pot...!
Cheers
George