Presuming you bought the through Paizo, you should send photos to firstname.lastname@example.org. If they’re defective they’ll organise replacements (sounds like you got a dud set - my expansion set is pretty close to the base set in terms of colour/contrast.
If you bought them elsewhere, you should return them via that channel (there’ll still be a replacement provided, it’s just it’s better if the chain of return follows the distribution network). That should work fine, though if it doesn’t Paizo will assist.
Customer service at Paizo doesn’t work at the weekend, so you’ve probably missed a reply from official staff until next week. The above might save a bit of time in the meanwhile.
Thanks for the thorough reply Steve. I usually get my Paizo products through local FLGS's, however the Forest Flip-Tiles sets were completely sold out from all the retailers in my area. I'm in Canada and it's pretty hard to find specific Pathfinder stuff; so I ordered it online from a UK based retailer two weeks ago and they only arrived yesterday. Due to this reason, there's a lot of hoops to jump through and I might have to pay return shipping. I was hoping to avoid this headache by contacting Paizo directly.
Since it's the weekend I'll have to play the waiting game regardless, and I've got no problems waiting for a reply on Monday. I've got around $1000+ worth of Pathfinder products and the rare times I've noticed a defective item, Paizo support has never failed me. Their customer support is truly the best.