help whit my new freesync monitor

[davip]

I bought an acer nitro vg270 monitor yesterday, and I noticed that whenever I turn on the freesync either at 165hz or 144hz any solid color looks like a crt monitor, its like the colors are subtly alternating between a lighter tone and a darker tone thus forming horizontal stripes in the solid color, more elaborate images with various colors in same pixel lines don't have this problem (at least it's not noticeable). if I have freesync off or stuck at 75hz the colors are normal. im missing something or is my monitor just low quality? I still have time to ask for a refund. sorry for my English, and lack of deatail, cuz i cant even take a photo of the problem

[jorimt]

I noticed that whenever I turn on the freesync either at 165hz or 144hz any solid color looks like a crt monitor, its like the colors are subtly alternating between a lighter tone and a darker tone thus forming horizontal stripes in the solid color, more elaborate images with various colors in same pixel lines don't have this problem (at least it's not noticeable).

Sounds like pixel inversion artifacts to me:
search.php?keywords=pixel+inversion+artifact