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.
"Having understood name-and-form, which is a product of prolificity,
And which is the root of all malady within and without,
He is released from bondage to the root of all maladies,
That Such-like-one is truly known as 'the one who has understood'." (Snp 3.6)
"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)