Ever since the Super Saiyan transformation was introduced, We've seen
Goku's hair vary from black to gold, to crimson, and finally, to gloomy. And Using a silver aura. Here is the most unusual hair color in each Goku's Transformation so far.
It is Not Just unique by its color, it is also unique because It Isn't
Goku's normal Super Saiyan spiky hair his foundation type hair. Additionally, It is Not classified as Super Saiyan since not only Saiyans can achieve Such a form. That Doesn't explain the reason why Goku's hair turned gray
The real reason might be because the Ultra Instinct is not really a form made for humans. It might be a feat to achieve for humans and GoDs alike, but it is very common among angels. Ultra Instinct might be the basic requirement for an Angel to be qualified to work with a God. For the GoDs, it would be their greatest feat and will open up the doors for being as powerful as their angels.
Goku's hair turned to gray because this Condition does Really the hair
Of anybody who achieves it into gray. That's why Whis and another Celebrities have silver hairloss. They have it eternally since they're in Ultra Instinct state permanently. He changed into that state.
It's rather obvious why Beerus along with another Gods of Destruction do not possess a silver hairloss. Along with the simple fact that nearly all of these are reptiles and cats, they have not mastered the Ultra Instinct yet. We have not seen two Ultra Instinct fighters may really have a struggle using a winner, however using Jiren along with Goku's struggle, we could actually see it.