The 14th Fennican Division has an unusual color scheme: the uniforms of troopers depend on their service branch.
Infantry & Cavalry : purple.
Mech Infantry: green.
Heavy Mech Infantry: black.
Reason for this is that WAY back, in the time of 1st edition Space Marine, when I had purchased my first IG box I only had two colors suitable for uniforms. I didn't want grey uniforms so I chose purple. Later I wanted some change and when I painted my mechanised company I painted the uniforms green and invented the "color coding" to justify the existence of different uniform colors in the same regiment.
The tanks OTOH still use the good ol' camo system. When I have time I'll re-paint my armor to the camo Finnish army used in WWII. See here for an example: http://www.andreaslarka.net/ps531008/ps531008.html
