The Low-/High-Tech rules for camouflage seem kind of bullshit.
(TL 0) Clothing similar to the terrain color gives +1 in that specific terrain. This seems reasonable.
Highly contrasting clothing gives from -1 to -3, which again seems reasonable.
(TL 6) simple camouflage is just a plain neutral colour which works almost anywhere and gives +1 to camouflage. So far, so good.
(TL 1) hunting shirt gives +1 for specific terrain, or +2 if given a 'blotchy dye job'. I'm dubious about this really being TL 1 and don't see how breaking up your outline and texture with foliage, cordage, fringes, etc. is no better than plain clothing unless dyed in a specific way.
(TL 7) Basic camouflage gives +2 in specific terrain and -1 or worse in all other terrain. This seems unlikely. Desert camo shouldn't do as good a job as jungle camo in the jungle, but it seems unlikely to be two skill levels worse than plain khaki! Something like +1 for reasonably similar terrain (e.g. forest camo in a jungle or swamp) down to -1 for contrasting terrain seems more reasonable. I also believe that there were some OK camouflage patterns available towards the end of TL 6.
(TL 8) advanced camouflage is even worse, giving -2 almost everywhere! This seems ridiculous; even very specific camouflage doesn't stand out that much in the wrong terrain.
Reversible camouflage is supposedly TL 8, but it dates back at least to TL 7, and I believe the Germans issued it in late TL 6.
There are no rules for effective universal patterns anywhere that I can find.
Overall, it seems that camouflage patterns are basically useless until you get to TL 9 and everyone should just stick with plain OD, khaki, etc.