Agreed and odd thing about that Kurama's chakra is suppose to be red but Naruto's KCM was also yellow as well as his bijuu mode.
That's most likely due to them not being in sync. Kurama mode, his pupils change.
Kurama influence via NES and a weak seal lets him tap into Naruto's emotions. If he's angry he passively succumbs to his influence.
I looked at the databook and apparently Naruto has three forms.
-Nine-tails chakra form.
-Kurama mode (basically Bijuu mode without the avatar)
-Bijuu Mode (Kurama avatar)
The way I see it, the rasengan was just a normal one and that the enton was the deciding factor in blowing up their arms.
I'm not saying Rasengan=Enton Chidori since on paper it should be stronger. If Sasuke actually hit him with it, he would have died.
It's just the way the two jutsu interact when they clash in combination with a new element. I think enton being introduced did more harm to both parties as a result.