This has likely already been recommended, but I might as well throw it out there.
You know those circles, on the map, that show areas you need to look in for your quests? I can't... see them? I have minor colorblindness and they just blend in with the background of the map. Generally, the only way I can find them is by scanning my mouse back and forth across the map until I happen to hover over it by chance.
Having the ability to change what colors are used would greatly help to make the game better for colorblind players. The colorblind filters available in the settings just aren't enough.