Don't have any pics of my reddish one, but here's one from the web:
The pattern on the sides of the main carapace, and the dark lines down the tail are fairly distinctive. Combined with the narrow claws, and I'd be 95% sure yours is Marbled without a better lighted pic.
Looks very similar in the pics. Wonder if P. Fallax might be one of the Marbled Crays original parents? They even have the same color range as Marbled (Blue->Brown->Red)
Here's a Fallax pic, compared to the Marbled pic above, they are obviously very closely related:
Have always wondered which cray species could be mistaken for a Marbled Cray, guess we know now.