Bad Dye Job
Try previewing them before you buy them. Dyes look different on different types of armor.
Each dye looks different depending on the material, the colors around it, and the lighting. The lighting in preview mode isn’t all that great.
There isn’t any way to “fix” the issue to everyone’s satisfaction, because there are too many factors involved. It would probably help a little if preview mode included some lighting options.
Your best bet is using the wiki (or other online resources) to see screenshots of the dyes on actual armor. Dulfy has a lot of the color palettes up and there are a couple of websites that use the API to offer you a widget that allows you a chance to see how the colors|armor would be rendered in-game.
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