I've had vendor liquids turn my wicks color - anything from a pinkish/reddish hue to vaguely orange. It seemed to happen more when I was vaping cheap fruit-flavored house liquids from a local shop right before I started mixing my own - haven't noticed it since, not sure if there's something about a certain flavor manufacturer or what that causes it. I also noticed having to re-wick a lot more frequently - with my own blends my RDA wicks easily last 50 ml or more, and I get 4-5 re-wicks out of a coil just by doing a good dry burn at every wick change.
I'm also using Rayon exclusively these days, and IIRC I was more of a cotton guy back when I was getting the discoloration, harshness, and need to re-wick constantly. I just got some cotton pads thrown in as a freebie with a recent
@Breazy_Com order, maybe I'll try them on my next build to see if it might be a wick material issue, but I've been vaping the piss out of my Crown tank since it came in, too lazy to build until the Velocity clones I ordered a couple weeks ago show up...
For
@ObxChef, if you're really wanting to cheap out now might be the time to try DIY - you can get a sample vial of nic from Nude Nicotine for like $2, some small bottles of PG and VG, plus a few flavorings and a couple syringes from either
@Roundhouse and Bull City or
@Donovan (ECX Flavor Lab) and E-Cig Express (my two favorite vendors) and have enough to crank out a few hundred ml of liquid for like 20 bucks. If you're vaping cheap house liquid like I was before I started it's probably single-flavor and really easy to replicate - I'm admittedly biased but I firmly believe we've got one of the best DIY communities on the interweb, check out the DIY subs and folks here will be more than happy to get you started...
EDIT: It occurs to me that since I've gotten lazy and reverted to tanks, I'm using cotton in those - I'm still not getting the discoloration OP describes, just crusty black crud that, when sufficiently accumulated, causes me to toss the coil.