Yes, Yellow-Sided Green Cheeks develop all kinds of different colors all over them as they mature; the most common colored "patches" or spots that show-up on the Yellow-Sided Green Cheeks are the shoulder spots that you're referring to here, and an orange/red patch on each side of their face/head right in front of their ears. Also, their bellies/chests change colors too, some more-so than other; usually their bellies and chests turn from a very bright red to a lot of bright yellow and even some tan. So you'll probably be seeing him change his coloring all over his body after he's done with his first really huge molt after going through puberty, and this is all completely normal for a Yellow-Sided Green Cheek...my Bowie is now 2 years and 3 months old, and he looks very, very different than what he looked like when I first brought him home at 12 weeks old...
