So yes PX8 is a solid Black with no pearl or Flake, and PXR is black with pearl and metal flake in the formula. Very easy to tell what one you have by looking at it in a good light.
If the flares are PX8 they will look ok on your truck if your truck is PXR but if is the other way around it will not look so good in my opinion.
Flat Black would look good on either color and since the flares are already painted black (as long as it is a quality job) you could clean, scuff sand with a gray scotch bright pad and use a quality aerosol to refinish each one. Just remember that the final finish is only as good as the prep work and substrate you are painting on.
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