That... should not be the case.
That said, in the pics I am using the ENB blue filter included with AA2.1, but that shouldn't make much of a difference.
If the trees next to the house in the pic (the one nearest to Sidorovich's bunker) are still brown and not yellow/red, then the textures weren't overwritten correctly.
Make sure that you have overwritten all the files in /gamedata with those included in the /gamedata folder of the addon and haven't accidentally put the addon into a subdirectory within the /gamedata folder (i.e. /gamedata/RealAutumn/gamedata/* would be wrong).
As this is just a simple texture swap, it should have zero compatibility issues and is definitely not dependent on using an ENB.
I hope that helps!
serialxt
B. joined
Polyglottal Idahoan with a passion for modding games past their limits in the never-ending pursuit of getting it "just right." I also like waffles.