Disagree on the juice matters, but I DIY. I deliberately go for non-colored flavorings and use sweetener, but properly. I can't vape much storebought before diluting and amending it heavily.
If you never give your tongue a chance to enjoy something else, I guess it would be reasonable to asses that flavor has to clog. It doesn't, and even the mixes I overflavor (for others) are usually not major coil cloggers. If you were to ask me why, I'd have to say I did not know, but my juices are rarely dark, and if they are, it's usually because some have been steeping a long while, but even using them, they are rarely dark. I even have a coco that I use that stays nice and white. Dark juices are either NETs or flavors with food flavoring in them. Dark is not necessary for flavor. Sweet MAY be, but oftentimes less than one would think. I will say that the NET I got my husband seems to be holding up nicely for him, but he isn't vaping ENOUGH yet.
Anna