The X* sets are based on presenting the armour and penetration values as numbers. X stands for XL, as in the spreadsheet, because I had to make a pretty complex spreadsheet to generate all the slope-effect armour values. C means "Coloured". "W" means "White". This refers to the colour of the text.
XC uses the CM1 colour codes for the numbers (red for paper-thin shading thru yellow to green to blue for mega-thick.)
XW is the RG-compatible member of the X* set, and all text is white or blue or yellow. However it is not just for colour blind people, but has been designed to hopefully maximise clarity. Thus the penetration numbers are colour coded for type of projectile (Yellow for AP, mid blue for HE, grey for tungsten, light purple for HEAT)
XW is my prefered option of the two X* sets, by the way. I find the colour clash of the XC set a bit too garish. Having said that, many people have told me they love it. So I offer both...
I'll update the readme for v2 to include some more detail.