The colour of Naruto‘s Rasengan
Naruto's own chakra color is blue, which contrasts with the Nine-Tails' own chakra color of red.

Interestingly though, despite Naruto using the Nine-Tails' chakra to create larger and larger Rasengan, the color remains the same.  This might be a plot hole; this may be indicative of Naruto himself performing the attack with a larger amount of chakra under his control.