There was an old mod that a guy named Chesthole made that redid a lot of the colors and tilesets of the game. It did not change that much of the basic look of the sprites but made the ground green and the buildings brown or beige. It was a cool mod, but it broke quite awhile ago as the game got updated, and new sprites and tiles were added.

Is there a way to update it for the current version of the Caves of Qud, and if not, is there anything similar?

I like the graphics of the game, it is just that the dark backgrounds compared with the sprites can cause eyestrain after awhile, and Chesthole's mod also made it easier to tell light from day.