From my seminar sheets I have taught over the years.

Colors
Crawfish coloration is what most anglers are interested in and studying local crawfish is a good idea. There is tremendous color variation from species to species and even within a species. Very little scientific study has been done on crawfish
coloration. These color variations are not by chance, but determined by their environments. Colors range from brown, tan, green, red, blue, black to sandy yellow and combinations of all these colors. A lot of crawfish in our area are brown or
tan with orange pinchers.

Another common color is black with metallic green mixed in, strongly resembling a junebug color. A number of factors influence crawfish coloration. When crawfish move from location to location, they can change their coloration to match their environment. This change doesn't occur almost instantly like in a chameleon, but takes hours and days to weeks. The potential for rapid color change could occur after molting. Dr. B. A. Hazlett of the University of Michigan found that a particular species of crab existed in two color patterns or morphs.
One morph was reddish-brown and the other green. Individuals were observed to molt from one morph to the other depending on diet. Apparently water chemistry and pH also play a role.
Crawfish have red and blue photoreceptors, which collect light from different wavelengths. In a Michigan study, Dr. Robert Thacker found that crawfish in water where blue-green wavelengths transmitted best were lighter in color. Crawfish
in water where red light transmitted best were darker in color. As you can see there are a lot of variables that influence crawfish coloration. The best way to determine the color of your local crawfish is to set out crawfish traps. These are
inexpensive and readily available. Bait them with carrots, hot
dogs without red dye, English peas, or pieces of potato. Put
them out late in the afternoon and check them the next morning.

What colors imitate crayfish? Crayfish bodies have light-sensitive cells called chromatophores that automatically adjust the mix of colors that the cells "expose" to the outside world, thereby allowing the crayfish to automatically match its color to wherever it spends most of its time. Their PRIMARY colors are shades of black, brown, green, or grey. On their pincers, their backs and lower fringes of the carapace, they have distinctive SECONDARY color accents, various traces such as blue, red, orange, white, yellow, or amber.
Just like the crayfish automatically matches its colors to its location, you should match your imitation craw colors to whatever color closely approximates the water color, the vegetation color, and the bottom and cover color of the area you are currently fishing. You can even micro-tune into the unique color of a particular weed bed, mud bar or crayfish-infested rock pile. As a rule, think darker - crayfish usually spend most of their time hidden under something or buried into the bottom by day. They usually come out to forage under darkness of night. There are two ways you can accomplish this "darkness" with lures. First, you can use opaque (non-see through) colors that are slightly darker than the water, vegetation, cover and bottom.
Second, you can use soft plastic colors that are semi-translucent (see through). Just pick a translucent color that matches the water, vegetation, cover, bottom color. As the translucent lure comes in and out of underwater shadows and climbs up or down in depth, the translucence allows it to blend into its background better. For example, when fishing tannin-stained waters or over reddish-brown mud or clay bottoms, you could try a jig 'n pig with an opaque pumpkin-orange skirt and a translucent pumpkin soft plastic trailer.
Summer Greens and Browns---When the days are at their longest, brown and green lures are at their best for bass. I start relying on darker-colored watermelon pepper/red flake lures in late June, and I phase into lighter-colored translucent pumpkins with gold flake by early July, and continue heavily with green and/or brown colors through August.
1) Days are longer now. So there is more light, causing underwater critters to lighten up their colorations.
2) Any lingering effects of spring rains and run-off have ended now, leading to lighter-colored waters with better visibility, therefore less need for dark, contrasting lures.
3) It's a veritable "green scene" right now with all the aquatic veggies at the peak of bloom. Therefore, most critters that hide in the water weeds should take on a greener hue now than at any other time of the year.