I have a Yoshi (Trixie) and a Birdo (Sunnie) so the collector in me now had to have a Koopa and well, introducing Kimberly! She went to Mushroom High with Sunnie and Trixie, graduating and pursuing her career in sports, always having an affinity for soccer. Her shell is magical, having been buffed by a Magikoopa she can take it off and use it as a soccer shell, changing colours accordingly, or hide in it and propel herself.
When on her back it's pink with purple "spots." When playing a serious game of soccer her shell changes to be black and white similar to a soccer ball. When playing a non-serious game of soccer the black spots change to pastel colours instead.