My idea is a normal type wild pokemon that possibly have 5 different ability. Each will let them transform into different color respectively in battles.

Red - Fire/Fighting
Blue - Water/Fighting
Green -Grass/Fighting
Yellow - Electric/Fighting
Pink - Fairy/Fighting

Also, there's a hidden ability that let them transform into

Black - Dark/Fighting

This will let some trainer to collect 6 of this pokemon with all different colour in a team

Please GF