I got it nice looking on my XL2540, actually the best TN panel image I've seen for color accuracy, the BenQ always comes with screwed up factory settings or presets for that matter but that's nothing new. The biggest difference obviously was the gamma setting which was set to Gamma 1 by default which made all colors very washed out, Gamma 5 makes they a lot more vibrant, borderline becoming on the dark side again but I care more about the image quality and don't play CSGO (I only watch it).
Color Vibrance 10
Low Blue Light 6 or 7 (to get more warmer color temp, closer to 6500k)
Picture Mode: Movie
This is with 144Hz and BenQ Blur Reduction on (ie. DyAC on XL2546) though, don't know how much it matters, possibly brightness needs to be set slightly higher if using 240Hz + DyAc.