Rogers is wearing a black uniform because, at that point in time, he was no longer Captain America.
The recently-resurrected ed Skull is tall, blond, and handsome, sporting a business suit... and a set of genes cloned from Steve Rogers. Within minutes, in the comic, the Skull is going to return to his old look, after suffering a face-full of his own "Dust of Death," which causes its victims to die horribly, their faces contorted to look like a red skull due to advanced mummification.
Before this happens, however, the Skull wanted to reveal his hadn in Rogers then-recent misfortunes. He even goes so far as to utter the following lines, which carry a bit more weight in-light of events from the past year or so:
For those that don't know, the Skull was recently responsible for the death of Steve Rogers, Captain America.