Welcome back to the skinning community Raven. Below are a few useful general sites. If there are any particular planes, air forces or theaters you are most interested in I may know some more specific ones as well.
For air force colours in general the nearest thing there is to the old Simmer's site is
Urban’s Color Reference Charts. The problem is this site is really geared at aircraft kit modellers rather than skinners. So you can navigate to a swatch showing you the colour you want but there is no RGB info associated with it. To get round this I usually just take a screenshot of the swatch, load this into my image editing software and use the colour picker tool on it.
For LW colours only the
Asisbiz LW aircraft colour page is pretty good. The rest of the Asisbiz site also has lots of info on LW planes and units, with lots of good reference photos.
There is a handy reference here for
USAAF marking layouts and dates.
For Japanese aircraft the research pages on the
J-Aircraft site is hard to beat.
For Soviet aircraft the
Soviet Warplanes Forums are a good source of info. There is also this handy
Soviet aerial tactical markings of WWII which lists the markings used by many VVS units during the war.
