You could use either "must" or "have to" in that sentence. There is no difference in meaning here.
There are other problems with the sentence, however. "Put on" is not the right verb : "put on" refers to the act of dressing, not of choosing what to wear. I agree with Tyler that "choose" would be a better verb.
Another problem with your sentence is the last three words. "Your trousers colour" (even with the apostrophe which Mr Zhang correctly suggests) is not natural English. It should be "...the colour of your trousers".
Also note that while "the color of your pants", as Tyler suggests, would be fine in an American context, it could be confusing elsewhere. For English speakers outside N. America, 'pants' means underwear.