The X byte of 32-bit color is nowadays used as the alpha channel (brightness), and is usually called A. But I'm not sure if Windows 95 supported alpha channels for display.
DirectDraw and Direct3D run on Windows 95 and both use alpha, so it's possible they could do something with it, but they also might just emulate it. It's been 27 years since I was writing video games for Windows 95 :p