I would say white is the hardest to read: "White Font"
brown/white comment background skips every other post, wait for a white background to comment white.
i know eye strain is an issue for some with an orange on brown background, but the skin wasnt done through css or phpbb, its all custom. theres seeing things like style statements and such done with inline parsed php spit from various code files if i remember right. phpbb doesnt support that, and just about any other phpbb source will loathe to even hear you talk about it because it changes things too much from what the phpbb codebase has ever been built to support.
i told the org i dont think it can be upgraded without loosing it, but the people who made the changes are no longer around. actually, ive heard twice about plans to upgrade eply's phpbb - both times i gave cameragrl a heads up thats not something you can just say "ok, lets do it." but i think they are irritated with me now saying i told you so.