I know the actual dress is black and blue. That's why I stated "the photo" instead of "the dress"
except the question is what color is the dress, not specifically, what colors/rgb values appear on the dress in the photo. If that were the case, you'd be seeing answers like blue and brown everywhere, since it would be as you said, that's the only choice to be made and no one would be debating whether the dress is white and gold or blue and black. but clearly, people are debating over what they think the color of the dress itself is from just seeing that photo.
anyway, taking the actual rgb values from the photo, you're essentially just hitting on a technicality and missing the entire point of why people are even arguing over the colors.