Pinks are tender and sweet. Browns are firm, though somewhat bland, and sometimes have a hint of iodine. It can be hard to tell the Gulf species apart. Cooked shells of all species are pinkish-red. Raw meats are translucent pink to gray.
Cooked meats are pearly white with pink and red shadings.
Don't pay white shrimp prices for brown shrimp. Brown shrimp have a groove in the last tail segment that is not present in Gulf whites. That's what processors check to tell what species they've got. Shrimp cooks in just 60 to 90 seconds at a rapid boil. When the meat turns opaque, it's done.