I've got a ton of Ariadna models that I've played over the last decade, but never really gotten painted. A few of them are 90% done, some have some splashes, and all are primed. I like to run vanilla, TAK, and USARF, and will probably dabble with kosmoflot when it is released. Anybody got decent ideas for making them look cohesive in Vanilla, but still distinct groups? The kilts help for CHA, but TAK and USARF are so easy to just blend together. Edit: I originally thought about doing a desert camo, but variations of khaki seem pretty bland.
What you're going to want to do is figure out a way that appeals to you to make each sectorial stand out from each other. For myself I've always described my Ariadna paint scheme as urban-ish; meaning that each sectorial has their own major color (Kazaks-green USARF-tan FRRM-blue, CHA-khaki/tartan) that features prominently but each one also features a variety of grays to bring a greater degree of visual cohesion .If you'd rather go a little more realistic camo then perhaps each one can use a different color more prominently, maybe USARF features browns more whereas the Kazaks have a lot more khaki.
Vary the camo (digital/night camo for one, verdant area green camo for another and urban for another) Tie it in with caps, coloured stripes on armour plates/jackets/accessories on belts etc
Paint armour panels for everyone in the same colour ( green for example ) and each faction uniforms in different colours.
I did universal gray armor and khaki pants. USARF got cream colored sweaters and brown leather jackets. TAK got green caps and green jackets. MRRF got black caps and black leather jackets. CHA will have kilts and blue jackets.
I do pretty much everyone up in the same camo pattern, armor color, and rigging/gear color. And vary what's left unit to unit. The color palette of the camo has changed a bit since I started, since it looking fine close up early on, but was too dark to make anything out from a distance. So I had to brighten it a couple times and dial it back a tad darker once.