I had a similar problem in Winter last year. In the end I wore some cream coloured pants and a white "hoodie" with a white t-shirt underneath. I'm not sure whether it was a no-no or not but during the meditation I actually had the hood on because it was so cold and as you can see from my profile picture, I have very short hair. No one seemed to think there was any problem with anything and earlier correspondence with the abbot suggested that comfort and practicality was as much a criteria as anything else... make sure you're warm, he said.
"Do not force others, including children, by any means whatsoever, to adopt your views, whether by authority, threat, money, propaganda, or even education." - Ven. Thich Nhat Hanh
"Whether I were to preach in brief, Sāriputta, or whether I were to preach in detail, Sāriputta, or whether I were to preach both in brief or in detail, Sāriputta, rare are those who understand." (A I 333, Sāriputtasutta)