First two pics are hard to distinguish. Generally I think knowing what base you're in should be
as obvious as possible based on wall colors alone. This is extremely subtle. In TF2 they use this beautiful color-bounce effect a lot (bright white spotlights on a red textured surface dimly lighting the faces around it - mainly the ceiling - with a reddish glow). Maybe you could experiment with some central, colored and sharply lit structures? Like a spotlight facing up right across the ceiling in the third pic. Most colored parts in your map are in the shade (not hit directly by any lights).
Third screenshot looks the best so far. With the textures changing right at the brush-edges the wall supports look a bit... polygony. I know TF2 goes for stylization, but screen 3 almost looks TFC. I think it's the different colors for different brushes that makes their low-poly structure so obvious, so maybe it just needs a more fluid transition between the red and whit/concrete parts?
I definitely like the direction the map is going, though. That looks like a fun ramp-room. Many good memories coming up and yet it looks fresh.