There's no way to really tell if it's common specifically for someone named Jojo. However, in general, reading fanfiction is a popular activity among fans of many different franchises. The Jojo series has a large and dedicated fan base, so it's likely that there are fans named Jojo who partake in reading fanfiction, but we can't say for sure how common it is without more data.
Supreme Emperor NvWa's Way was a fantasy novel written by Saint Emperor NvWa. This novel told the story of an archaic god. The protagonist conquered the world on the road to becoming an emperor, laughing arrogantly. The plot of the novel was full of ups and downs, and the writing style was excellent. It was praised by the readers. Supreme Emperor NvWa's Way was a work in series, and there were currently 519 chapters in total. Other than that, no other information about Sage Emperor NvWa's other works was provided.
Perhaps this Jojo is interested in exploring different interpretations and stories within the Jojo universe that fans have come up with. Fanfiction often takes the existing characters, settings, etc. from the original Jojo series and creates new and unique storylines. So, this Jojo might be a big fan of the series and wants to see what other fans have imagined.
It depends. Maybe there are some telltale signs or elements that suggest it's a JoJo reference fanfic, but without specific context, it's hard to say for sure.
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.