What foods would cause a PP to actually BE purple?

[Zombie(:]

...because the other day, i got a new hermit crab, and he is the most beautiful shade of dark violet ever! i had to have him :3 as of right now hes trying on diff shells besides the ugly one i bought him in... is there any specific reason as to his sort of unusual pretty coloring? i could post a link i found of a similar looking one i found on google~

[emmac350]

Crabs' coloring is a little tricky to maintain. Generally speaking, you can't just feed your crab a purple food to make him turn purple. However, if you follow the guideline of bright or dark foods (naturally bright or dark) you can try to help your crab maintain its color. So bell peppers, spinach, pink seafood (like shrimp), etc. - basically, the brighter or darker the food is, and the more varied his diet is with those bright/dark foods (not the same food over and over) the more likely you are to get the coloring you want. My PPs had more purple than their claws (I called them "racing stripes" going up their legs of purple) but they weren't all purple. I attribute the coloring to the Astaxanthin powder I put on their food nightly since they had the coloring a few molts after I started offering it.