I like this idea; it would absolutely add to the diversity of avatar customization. As you said, some avatars would go very well with these colors. That being said, it shouldn't be top priority right now as an update was just released with two all-new colors as well as an updated yellow background. The Developers are now focusing on other features, and possibly even ACC 2.0.
However, this would be fairly easy to implement so I don't see how this would present an issue once the Developers get the time for this addition.
Also, you might want to take a look at this thread to see what they could look like!