Why does Jojo change art style?

“I put a conscious effort into creating distinguishable protagonists who don’t have similar silhouettes and appearances, including their outfit designs,” Araki said. “I also have the protagonists function to symbolize the ‘world’ that each part takes place in, so the story influences them as well.

Is there officially colored Jojo?

The series adapts the majority of the manga with fully colored panels, ranging from Phantom Blood to JoJolion.