This is very common in pigment coatings and paints. It is called metal marking and it is a characteristic that is very difficult to eliminate.
You can even see it in dinnerware like white plates. We usually test with wedding rings and forks. It a constant focus and improvement project for General Finishes, especially the whites. The difference with tinted clear is that the amount of pigment varies from color to color, so sometime it will occur with the lighter paints.
      
  Enduro Water-Based Conversion Varnish
  Enduro Water Based Stain Blocker Primer
  Enduro Water-Based Tintable 2K White Poly
  Enduro Water-Based Pro Series White Polyurethane
  Hard Wax Oil & Hardener
  Gel Stains
  Pro Image Flooring Topcoat
  Jen Poly Brushes
  Stir Stix
  Ultraflex Softback Sanding Sponge