Original Dungeons and Dragons made it easy to tell which elves are the Evil ones – they’re the Drow, the ones with the coal black skin. Whilst this might have been more socially acceptable in the 1970’s when the first edition was published, most modern gamers tend to shy away from that specific form – even those who are otherwise happy to have “evil races” be easily distinguished by their form.
It might seem useful to backtrack the appearance of elves from DnD back to Middle-Earth, and so to the mythic originals from which Tolkien drew his inspiration. Unfortunately it’s not. The Norse sagas have two kind of ‘elf’ – the lios-alfar, which are your basic elves, and the svart-alfar, which are dwarves. Arguably the Vana might be the inspiration for the High Elves, but the distinction between Quenya and Sindarian is largely linguistic rather than genetic, and the Vana are more close kin to the Aesir (both are Norse gods) than the Alfar (who are just elves), so I’m guessing not so much.