In what i think of younger old leaves, that are still green, the spots are dark gray, in oldest leaves, that become a bit yellowish, some spots do get a reddish tinge but not all, mostly they stay gray.
Nothing is raised, the leaves are smooth
I think that leaves, that have grown in my care dont have (as many) spots, and since the lighting is quite certainly weaker, it may as well be lighting.
The other thing i think is quite possible is some kind of (semi)symbiotic fungus, that lives and fruits in the leaves. If it'll keep getting these spots, i'll check microscopically, as it should be interesting, because it really does not seem to bother the plant, at least in think so, as it flowers and grows quite abundantly.
This plant is my favourite
. The flowers and habitus are beautiful, I'm already choosing the next restrepia with my sister