Why is Trunk's hair blue and why is Vegeta just Krillin now?
Real reason? Trunks' hair was always supposed to be the same colour as Bulma's. In the manga they were both purple, but the anime changed Bulma's hair to green/blue/everything in between, but kept Trunks' hair purple for some reason.
Toriyama has been trying to fix this for years, but since Toei wouldn't change Bulma's hair back to purple (except in the Path to Power OVA), he started drawing Trunks with blue hair instead (Kid Trunks has it in his Battle of Gods reference sheet for example).
Now, why did Toei finally give in now, but only with Future Trunks? Because if he's going to be sticking around as part of the main cast, he's going to need something to set him apart from main timeline Trunks if they ever do a timeskip.
And Vegeta has been the prince of all jobbers since Z. It's nothing new.
If Black isn't Zemasu, then who the hell is he?!