Let me chime in with EVERYBODY else--you don't need to deal with this (it will leave you with a bad taste in your mouth for growing orchids .)
I can't say they saw you coming--it was probably on its way to turning yellow when you bought it.) Just take it back and get something healthy that is going to boost your confidence in your ability to take care of Phals. They are, in my opinion, one of the best orchids around
Good luck from here...
