The JoJo manga is mainly in black and white. Colored versions exist but are not the norm. Sometimes, colored illustrations are done for promotional purposes or by fans.
The Jojo manga is mainly presented in black and white. However, there might be some special editions or fan-colored versions out there, but those aren't the official ones.
The Bleach manga is not colored. It's common for manga to be in black and white to focus on the line art and storytelling. Color versions might exist in certain promotions or adaptations, but the core manga is monochrome.
Generally, manga are black and white. This is mainly due to cost and production time constraints. However, some popular series might have colored pages for special chapters or volumes.