There were a lot of things that people liked about the Dragon Ball Super movies and anime series. Not the least of which was that it was the return of the Z-Fighters in a way that was both modern, fun, and not GT…at all. In fact, they basically retconned that series to go and make this one, and most fans don’t mind that at all. It was through this series that we got to see the arrival of the God of Destruction Beerus, that we got to see the return of Frieza in all his terrifying glory (and a new form to boot), that we learned about the Dragon Ball Multiverse and all the dangers that are still out there for Goku and his friends to face. And of course, we got the arrival of Ultra Instinct.
After all, Dragon Ball Super wasn’t going to let Goku’s power level just sit at Super Saiyan God and Super Saiyan Blue, was it? Oh no. During the Universal Survival Arc, Goku (via his fights with Jiren) was able to unlock a kind of mental focus that let him fight without needing to think. It was nothing but pure reaction, and it was known as Ultra Instinct. Though it should be noted that in the tournament it almost killed him, and he wasn’t in complete mastery of it even at the end with everything on the line (which led to him and Frieza teaming up to beat Jiren so Android 17 could be the last one standing).
However, that doesn’t mean that the story ended there. The manga for the series is still going, and in it, Goku and Vegeta have each gained new levels of power (Vegeta got Ultra Ego that he’s still learning to master himself) and that includes getting new master on Ultra Instinct for Goku.
Because while he can now tap into this power at will after some massive training, Goku has tried to “experiment” with the form in order to find a balance between what it is, and what he is. Including in one key fight him not going silver-haired in the form, but keeping his classic black hair look.
This confused many people, so Dragon Ball Super manga artist Toyotaro revealed the truth behind what is going on:
“The reason why Goku ultimately chose to go with the black-haired form this time is because the silver-haired one cannot be maintained unless the mind remains calm.”
With the black-haired, he still has the abilities of Ultra Instinct, but doesn’t need the full-on focus that the other versions of it requires. Toyotaro says he feels that Goku is slowly learning all of the ins and outs of the form so that he can become even stronger with it.