I will take a pic as soon as I can find them. I just got home from vacation and I have a snail problem now.
So in cleaning up the mess that was made by going on vacation (that will teach me) I have not been able to find any of the baby purple shrimp. This could be because I just have not seen them yet or they might not have survived the ammonia spike caused by some dead plants.
I see brown in this picture as well. I *have* seen strange colorations, including purplish. From what I've been able to gather, RCS coloration is probably caused by more than one gene, each of which might have multiple different alleles. To get a clear picture of shrimp genetics, the way Mendel did with his peas and other plants, would most likely be the work of many years. One would have to get many lines of purebred (read: inbred) shrimp and *very* carefully cross-breed them so as to make sure the actual parents were known. This would likely necessitate hundreds or thousands of individual shrimp containers with a known female and a known male. All of the offspring would have to be counted and their phenotype recorded. Rinse and repeat for the F2 generation and further down the line.
This doesn't even begin to include the possible interactions with the environment or epigenetic influences (these are related to DNA, but are not DNA-based; things like transcription factors, enzymes, etc.).
To get a clearer picture, the best way to go nowadays would be to interest a population genetics research scientist, preferably one with a few grad students and a decent budget (harder to find anymore) and get them to generate either 1) a RCS Single Nucleotide Polymorphism (SNP) profile, or 2) a fully annotated and comprehensive RCS genome map. The first is cheaper, but doesn't necessarily explicitly tell you what genes are acting. The second could tell you what's going on genetically, but would be much more expensive. You can get a full genome on an individual organism for the low thousands of dollars, but here we're talking about getting genomes of *populations* of shrimp.
There has actually been "purple" (heard it's usually just red flesh, blue shell making it appear purple) freshwater shrimp, just a very rare occurrence and has yet to breed any sort of stable line. Maybe even the blue color would darken to black? Don't know as I haven't had one nor heard or seen much about them.
Here is a thread discussing purple shrimp for those interested. PURPLE SHRIMP Impossible? - Genetics and Selective Breeding - The Shrimp Spot
There are purple saltwater shrimp though, so that's cool