carrots are not naturally orange but originally purple...in the 1500's the Dutch enamored with their royal family developed orange carrots to honor the family colour of the royal House of Orange ...
read this in an food article yesterday...purple is making a comeback with chefs, slightly different flavour sweeter apparently...I don't recall anything about nutritional differences...
http://ecobites.com/eco-news-articles/organic-gardening/1959-purple-carrots   Modern orange carrots have always been known as an excellent source of vitamin A and phytochemicals including carotenoids, phenolics, polyacetylenes, isocoumarins, and sesquiterpenes.     But the ancient purple carrot has double the level of beta-carotene than the orange carrot and contains 28 times more anthocyanins.   Anthocyanins are potent antioxidants that give vegetables their red, blue and purple colours. But more importantly, they capture harmful free radicals in the body, slow blood clotting and act as an anti-inflammatory agent.       Recent studies have shown that these benefits as well as other antimicrobial and anti-carcinogenic activities can help and prevent cancer, heart disease, stroke and diabetes.
Burpee's sells carrot seeds of all colors. You can get purple, orange, red, yellow and white carrot seeds from them.
They don't help you see in the dark, though. That was a piece of British wartime propaganda to explain away the nightfighters' high success rate in finding enemy bomber flights, which was actually due to the top secret radar.