in the opening we see him fighting in his base form, then he goes to super saiyan (i'm pretty sure his eyes flashed gold for like half a frame (sarcasm) while he was going super saiyan), then he goes super saiyan blue. i know it's just the opening but sometimes they like to put little easter eggs in their opening, so this might be relevant. it seems like goku is putting out a lot more power than usual in these transformations, especially the super saiyan. whatever, anyway...
after he goes super saiyan blue in the opening we see him like he's powering up even more in red aura. i think this could be two things. either it was just symbolizing him using kaioken to boost his power very quickly, or he was attempting to reach a different form.
it could be either, but i like to think he's attempting to reach a different form. after the red aura explosion we see him emerging from the red aura. his hair is black but his hair style looks like the super saiyan hair, and he has a steam like aura around him. if it's symbolizing a new form then it will either be ultimate goku or a base god form.
![Image](https://s29.postimg.org/jqs8035o7/000000000001111111111.png)
of course, it could just be hair physics, and the steam could just be symbolizing after effects of kaioken overload. in the next scene we see him battling like normal again.