The app itself is free to install. However, depending on the specific manga you want to read, there could be charges for accessing certain volumes or chapters.
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 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.
Mangatoon is worth trying. It has a decent collection and provides a smooth reading experience. Some of its features like bookmarks and recommendations are quite handy.