Posh Etiquette Question

Hello! I have been purchasing on and off of PM for a bit now. Just received a scrub top that doesn’t seem to be the right color. I bought a pair of pants off amazon to match, which have the tag with color name on it. They both arrived today and the top is significantly darker (though still part of the same color family).

I wanted to ask the seller if maybe there was a mix up but cannot find a message section. How do I contact them without opening a case right away?!