I tweaked colours and now they are looking better IMO. I also turned off motion blur, depth of field and bloom. I wonder if to turn on OpenAl, but I don't know what is it. Now I found nice balance between good graphic settings and visibility of enemies, thanks.
I was playing on very low settings, and now with my new pc I am playing on max graphics setting :) That's true, more maxed up graphics = more distractions and it's harder to spot enemies. But on the other hand... my UT3 looks better than yours