No coconut oil wouldn't fade your hair it will actually lock your color in. There are so many different products to buy, shampoos and conditioner that maintain your color, Head and Shoulders is known to strip any hair dye from your hair so avoid using that.
I would think an oil would darken it at least temporarily. Your hair fades because sunlight is a very good bleaching agent.
I'm really interested in using it but not if it fades out the hair dye.
I don't think it can fade your hair, it mostly nourishes your hair you can also look here if you wanna know what is the best kind of Coconut Oil for hair