Black Paint Bowser is the final boss in Paper Mario: Color Splash. He is basically Bowser covered in Black Paint.
Appearance
Start And Middle of The Game
He is an Black version of Bowser, with no differences of his body.
End Of Game (Battle 1)
He looks fairly the same as Start And Middle, but his eyes glow, with his pupils showing.
End Of Game (Battle 2)
He is bigger, his body looks the same as Battle 1, but bigger and without the pupils, making him look even more evil.
Story
Black Paint Bowser stole the paint stars, and scattered them everywhere. It was Mario's job to rescue them for Port Prisma fountain.