This is one of the key aspects of the case. The color of the pixels in the image is clearly blue. That's irrefutable. We can do a quick color analysis to figure that out, as you did.
But, unfortunately, that doesn't answer the question of what color the dress itself is. Just because the picture shows it as blue doesn't actually mean it is blue, and there are numerous illusions, color correction issues, or optical afterimage effects that could cause something that actually is color A to appear as color B, either to the camera or to us.
I'm firmly in the "the dress appears blue and brown/black but is actually white and gold" camp. There are numerous highlights in the image that cause the true color to pop out from under the blueish pall that is over the whole thing. You can see a more true gold up on the right side of the collar and along the top edges of some of the ridges. Likewise, you can see a truer white in various places where the light hits it more directly. Whether it looks blue and brown because there's something blue behind the camera that is reflecting a blue pall over the dress, or it looks blue and brown because of the white balance being out of whack on account of the massive backlighting going on, I don't know, but there's plenty of evidence in the image to suggest the dress itself is white and gold, even if it doesn't immediately appear that way in the image.