This happened to me too. I bought a pair of Chanel flats and the seller advertised it as being black but when I took it out into the sunlight, it was definitely blue. I also have black Chanel bags that I can swear that it's black but again, in the sunlight it's blue. Chanel's blue and black colors are very similar so it's easy to get the two colors mistaken. Like the others said, take it into natural lighting and take a pix of it next to something navy.