Just a thought worth consideration... 35+ years ago I had finished the inside of my house. The place was about a hundred years old when I started and I gutted it, then fixed it up. I discovered hardwood floors under luan plywood - nailed every six inches, then covered with roll vinyl flooring.
(Yeah, it was a dump when I bought it - but it was what I could afford) The floor finishing guy suggested dark stain to hide the nail holes. It looked great. Then he suggested a a satin or matte finish. That looked great too when he finished!
ANYWAY, getting to the point: That dull finish on my floor was great for about six or eight years. Then the wear patterns started showing up. Asking questions, I was told that a satin or matte finish was created with laquer thinner or (insert your thinner name here) something similar.
It isn't as durable as a high gloss finish. "It is softer" is what I was told.
Just guessing, but I would imagine the same thing happens with imron or any other good grade of paint.
I agree with @
hndrsonj that given time, the sun will dull it Just my two cents and RapCo has the color for sure. If there is something other than a thinner that a paint mixer can add to it - it has a much better chance of working (in my opinion).