There is a wendtii red which is dark chocolate brown on the upper side of the leaf and a deep red on the bottom side. I once had a cordata variety that was quite red in good light. (Don't have it any more) Oliver Knott gets spectacular red undersides with Crypt wendtii 'Mi Oya' as shown below:
Almost forgot: there is a reddish brown variety of C. albida.
I find that with Cryptocorynes and other Aroids, not only within species can there be lots of variation, but the same plant, identical DNA, grown in different conditions will have very different leaf forms as well, so it can often be tricky to tell for sure without the spathe.