I'm being genuine. I know he had blue arms in Sonic boom and I hated it there too. The peach colored arms accomplish 3 things:
-They make Sonic appear more human subconsciously and thus more approachable.
-they make the design feel more open and free. For example compare a tank top to a long sleeve shirt.
-they segment the body and make it easier to appreciate the individual parts of the design better.
It's a small issue sure, but it's still one that greatly bothers me. It'd be like if in the Mario movie Mario doesnt have a white circle with a red M on his hat but instead just a red hat with a white M; small but a distinct difference that's hard to ignore.