I like experimenting with camouflage, so I take inspiration from looking at things like aerial/satellite views of Earth and other planetary bodies and trying to think how I'd mark a military unit serving in that area. It's not really so much about HIDING a three-story-tall Battlemech on an ice field on Jupiter's moon Io, it's about breaking up its outline so it's harder to get a clear shot at, after all. Another source of inspiration, dovetailing into the first, is how military units of the past 100 years disguise armored units in Earth's terrain- for example, the Swedish Air Force used a fascinating scheme on their AJ-37 Viggen fighters in the 1970s/80s that allowed them to blend remarkably well with their country's terrain. Same for the 1940s Luftwaffe in North Africa, who could make their planes all but disappear if looking down on them against the Sahara.
Parade schemes are nice, and I do find myself digging in the old Field Manuals and Camospecs for inspiration on those sometimes, but I much prefer an 'in the field' look usually. And if all else fails, three-tone grey urban camo never fails to make something just look mean as hell. ^-^