I asked a question about grey or blue shoes look better. I mentioned that I am wearing jeans most of the time.
This is one of the answers:
"If they are blue jeans then I like the grey ones, unless you are trying to match."
What does it mean? Does it mean the grey shoes can match anything that you wear? or Does it mean that the grey shoes only match blue jeans?
The final part of the sentence, "unless you are trying to match", refers to your opinion about matching blue jeans and blue shoes.
He/she suggests that you wear grey shoes unless (except if) you want your (blue) jeans to match your (blue) shoes.
You can't get a job unless you've got experience (= you can only get a job if you have experience).
Unless you call me to say you're not coming, I'll see you at the theatre (= I will see you there if you do not call to say you are not coming).
(Definition of unless conjunction from the Cambridge Advanced Learner's Dictionary & Thesaurus
© Cambridge University Press)