Here's 2 options you can try: 0E4B24 is the game's "official" Green Lantern Corps Green used on all of the GLC NPCs. The only trouble is, it really only looks right on the NPC GL Corps uniforms, with their specific texture. On almost all other fabric/material textures in the game, it looks too blue. A better alternative for Player Characters is the one that myself and a few others recommend, 00510C. Unlike the Official GLC Green, it looks good on MOST textures in the game, which made it ideal for use on one of my characters, Stel of Grenda. Here you can see Option 1 on the right on the GLC Reservist, and Option 2 on the left on Stel: Hope that helps.
You can try some of these; they're pretty good https://forums.station.sony.com/dcuo/index.php?threads/heroes-colors-codes.240898/
