I think the best way is to fax it to your college.
By right what you wear is up to you unless it's stated in the company policy that you cannot wear all black on the first day of work.
However, if you are unsure whether you boss will be offended ... you can be more defensive ... wear some other shirt ... don't tell me you only have one set of shirt and pants???

I think it's time you learn to think and make your own decision.