I was reading Halichos Bas Yisrael and came across an interesting point: "Bright red clothing is considered immodest." It was then grouped with tight clothing (which is an interesting line in itself!). I had heard that "bright red" (as distinguished from shades like "burgundy red") is considered an immodest color before, but primarily from people stricter than your average modern orthodox community. Of course, some communities go further, and the women traditionally only wear black, white, and navy blue. I would be thrown right out of those communities because I love wearing very bright colors!
The book cites this to the Shulchan Aruch, Yoreh De'ah 178:1, which is not a resource I have in my home yet. I'd appreciate it if someone could tell me what that says! The footnotes in the book go on to describe that the prohibition has several sources: (1) the prohibition against adopting pagan practices, especially "licentious" ones (anyone care to explain why this was a licentious and pagan practice?), (2) the tradition of "modest women," (3) red is associated with arrogance, and (4) Rashi, commenting on Bereshit/Genesis 49:11, says, "Their clothes have the color of wine...and are worn by women to entice."
I have been having a similar discussion in my personal life about the line between a chumra and mandatory "minimum" halacha, and it does seem to be a different line for every person. As the old saying goes, "Anyone stricter than you is a fanatic, and anyone more lenient than you is a heretic."
What do you in Lurker Land have to say about women wearing red and the chumra/halacha line? I would very much like to hear from you!