In The Comics
Jason is the twin brother of Cheryl Blossom and, naturally shares her (and the rest of the Blossom family's) red hair. For the most part, he's also every bit as vain as his sister.
In The Show
Jason Blossom is exactly the same in terms of looks. However, you only ever get a good look at him during flashbacks, as it is his murder that is the driving plot point behind season one. Apart from that, he's mostly just shown as a cold, rotting corpse.