This is a semi fictional skin - the painting in dark grey/bright grey as used by the first prototypes of the russian SU-50 / PAK FA was really made by VFC-111 "Sun Downers" as you can see in the screenshots. But i added the typicaly Sun Downer "Decals" to this skin - like the sun on the rudder and the shark mouth on the nose - i also gave it some used look...
Crediits: Sun Downer Helmet and most of the Techmarks are from "KIZIR_77" - so thank you for the permission to use your great stuff!