This year I grew a variety of purple carrot called "Deep Purple".
It was pretty fun seeing purple carrots. I thought the kids would love them but they were a little freaked out by them at first.
When you boil them, they turn the water purple. Their color fades a bit with cooking.
They taste just like regular carrots. I don't think I'll grow them again though for several reasons. First, they didn't grow well in my soil. They split, forked, and otherwise twisted where the other varieties of carrots I grew did much better. Second, most of the purple carrots had a tough, fibrous green core that was almost inedible. I'm not sure if I left them in the ground too long or if they were supposed to be that way.
So, it was a fun experiment but I think I'll stick to my tried and true orange varieties.