The majority of manga are not in color. It's a common practice in the manga industry to use black and white for regular publications. But for certain limited series or special projects, color might be employed to make them stand out.
The JoJo manga is mainly presented in black and white. However, there might be some special editions or colored illustrations for promotional purposes, but the standard version is not in color.
The One Piece manga is not in color. It's presented in black and white, which allows for greater focus on the linework and details of the illustrations. Colorized versions might exist in some limited cases, but the majority of the manga is black and white.
The One Piece manga is mainly presented in black and white. However, sometimes there might be special color editions or promotional images released, but the regular series is not in color.
Well, start by choosing the right tools like quality colored pencils or digital painting software. Also, study color theory to pick harmonious combinations.