Sam2 and Josh31 –
Please. Let’s be honest, we all know that the halacha found in OC 53:18 is not relevant to this discussion. It has as much relevance as do white shoelaces, v’doik.
You want a makor? Yoreh Deah 178:1 in the beginning of the Rema. ??? ??? ????? ??? ????????. Personally I don’t think that one needs to wear a white shirt and black pants to satisfy this inyan, but the ones who say you should aren’t coming from nowhere.