Hi little critters,
Looks to me like classic vitamin A sparing. Crayfish are blue like that when they do not have enough vit A in their diet, the deficiency is caused by the limited algae provided in their diet (that contains beta-carotine). Crayfish have limited ability to produce vit A themselves, hence they do not waste what they have on pigments- therefore the blue colour shows. Farmed prawns are fed a finishing diet that is high in beta-carotene to give them a brilliant red colour before market. The so called "selectively bred" thing is a sham. There are pelleted feeds out there for redclaws in particular, to get him back to normal. As for the no moulting, depends on water temp and how much you feed them. Hope this helps (even if it is late).