Color as a StructLayout

This is a proposition to turn color into a StructLayout (equivalent to unions in C).
It would be nice to have since it makes manipulating Colors a bit faster.

Can people please check this on other platforms to identify any endian issues?
So far it's tested on:
x86 (AMD Phenom II / Windows 8 / store app)
Snapdragon ARM (S4 APQ8060A / Windows RT / store app)