What's this mod about?
This mod simply changes the color palette for the German rally by largely removing the yellowish tint from the sunny/midday condition. Other times of day/weather conditions either in Germany or other locations are not affected.
Extract the >postprocess< folder inside the option of your choice into the main directory of DiRT Rally (by default [X]:\steam\steamapps\common\DiRT Rally). When prompted to overwrite go ahead, I've included a backup in case anything goes wrong or you just want to go back to the default color palette.