You would think it's be pretty easy for him to do an 8:2 ratio. Presumably, he can make up to 9 Tailed Beast arms. He should just channel blue chakra through 8 tailed beast arms, then red chakra through his own two hands.
I suppose he technically said Positive Blue and Negative Red.
I want to see a Tailed Beast Ball made of Naruto's Chakra, Kyuubi's Chakra and Nature Chakra!