Dear Blue Lobster:
We have an Electric Blue Lobster. He's gone through at least two molts and is if anything a much richer, deeper blue (with bright red spots in places). Does this mean he has not been artificially injected with blue dye?
Dear Gentle Sir:
Though cray owners usually complain of the opposite—their cray's colors fading into disturbing shades of slimy brown-green-grey, factors that don't include unnatural dyes or make-up can cause a cray's colors to become brighter and more pronounced.
Lighting is important. Despite being a bottom-dweller, crayfish are used to and require regular doses of sunlight throughout the year. Without this exposure, they fail to form vitamin D and other compounds necessary for robust health. With crayfish, poor health means poor color.
Your substrate can also affect your cray's coloration. Like any animal, the cray will try to blend in with its surroundings, and like some specific animals, the cray can change its coloration. If your gravel is bright, your cray is likely to become brighter over the course of several molts.
During some species' mating phase, the cray may ingest local minerals or plants to augment their look. This serves to make the cray more attractive with specific muds causing reds, blues, or yellows come out in their shell. Some species even wear algae or fungi as wigs.
Keeping a picture journal of your cray can help document its color changes. Whenever you perceive a coloration change, use your favorite webcam to take pictures. Then upload the pictures using your favorite blogging software and you can over time adjudge the what, if any, change has occurred.