This page is a bit of a cheat really! Making an RGB Scart Lead for your SNK Neo Geo AES is pretty much the same as making one for the Sega Mega Drive, except that the 8 Pin Din plug is slightly different. (Once I’ve migrated my Mega Drive guides, I’ll link to them). Some people try to use the same cable for both consoles, that can damage the cable though, or worse, damage a console.
I use Tim’s site for the correct info on wiring up any game consoles RGB Scart Lead now, it’s the best I’ve seen for this info.
It is possible to buy a cable that is already wired properly, you could try Retro Gaming Cables – use the code MMMONKEY for 15% off!