In short: Metro looks different because it uses different colors. I guess this shouldn't impact readability or accessibility in most cases due to the use of simple, sharp icons and white text. But I guess the white text could result in problems when the color blind perceive a given color as a light gray, resulting in little contrast.
Thanks for the information and the link, that is a really cool site! I'll make sure to use it on future projects just to make sure I'm not completely screwing over color blind people.
Deut. (red/green) here; it looks fine to me. In my case, most colour-blindness issues arise from poorly contrasting colours - given that most of the Metro style is white text on a solid bright/dark (not pale) colour I don't see many issues.
http://colorfilter.wickline.org/?a=1;r=;l=9;j=1;u=aozora.git...
In short: Metro looks different because it uses different colors. I guess this shouldn't impact readability or accessibility in most cases due to the use of simple, sharp icons and white text. But I guess the white text could result in problems when the color blind perceive a given color as a light gray, resulting in little contrast.