Is a man allowed to wear garments that are red?
It is technically permitted, however it is preferable even for men (and the custom of some people) not to wear red garments. The reasons why Jews stay away from wearing red garments is because it used to be the custom of the gentiles to wear red, and there is a prohibition to go in the ways of the gentiles, “u’bchukosayhem lo teileichu”, secondly it is a loud color and not in line with dressing modestly. A third reason applies to women, because red clothing are enticing and attract undo attention. The first reason doesn’t really apply nowadays as it isn’t the custom of the gentiles nowadays to dress in red clothing. The third reason doesn’t apply to men. However the second reason would still apply.
Shach Y:D 178-3, Drashos Chasam Sofer 2 pg. 244b, Darcei Tesuhva 178-16, Divei Chachomim E:H 46-2 in the name of R’ Y. Kaminetsky zt”l, Chashukei Chemed Becoros 44a.