I prefer Green, I'm just going to call her that because that's what I grew up knowing her as, as opposed to Blue. I've always liked how crafty she is, and her backstory really stood out to me. I especially liked what they did w/her character in the FR/LG story arc and G/S/C arc, as well.
Red is okay, I never had any problems with him as a character, but R/B arc Red wasn't my cup of tea, I liked him a lot better when he wasn't the spotlight character, ngl. Well, I did like him as a main chara in FR/LG, though, just not in the R/B chapter.
Eh, Blue is cool, and a lot less arrogant than the game counterpart, but I liked other rival characters (Silver, Sapphire, etc) more than him. He did mature quite a lot, though, which is cool.