I've been playing ADOM for years with no real issues regarding color (unlike many other games that fail to take colorblindness into account, a deficiency that affects a sizable population). Lately, however, with NotEye and all the enhancements that have been added (including the health bar and the border-color hostility marker), a toggleable "colorblind mode" featuring visual changes for easier usability would be a good idea to consider.

A few suggestions:

-Some items are difficult to see, due to blending in with the floor. Maybe give all items on the ground a "halo" around them (either permanently, or for a brief period of time for newly dropped/discovered items) for better differentiation from the ground.
-The new "hostility" border colors are a great idea, however I personally can't tell the colors apart very well as it currently stands. Maybe friendly could be a bright yellow, neutral gray or blue, and hostile can stay red?

Alternatively, the changes mentioned could just be implemented in the base game to remove the need for a separate colorblind mode.