Marbled Crayfish diet

so i hadnt seen my marmokrebs for 2 weeks. and when i went to go pick them up last Saturday they had an obvious blue tint to them. im not sure what has changed, but i figure my roommate may have overfeeding the tanks over the course of 2weeks

i figure its diet because the largest ones have the most blue and the smaller ones are more muddy colored still.

does anyone have any personal data linking a causal relationship between diet and coloration?

Mine , which yours are related to , don't get "blue " tints . As they get older they get a greenish hue and a couple have a light turquoise tint . A freind of mine has some down in Tennessee , has some that are 50/50 . some grow up to be mottled green/brown . And some grow up to have obvious blue coloring .
Ray

maybe its diet then. i use a mixture of Hikari Cichlid Gold and Cichlid Excel for the crays. along with spinach and zucchini