Alright, I went back and compared two screen shots. The color palet isn't that different, but the screen shots on Grim Dawn do seem to have more texture. If Diablo 3 screen shot have more texture, they should look fairly more grim. Without texture, the world of Diablo 3 looks very smooth.
I took this screenshot to compare
The rocks don't have that same crisp detail as in the Grim Dawn's screen shots.