Each layer in color film only makes one color and it is always fully saturated because there is no other choice. The density is the only variable I see.
Balancing the exposure of the layers is another story because each layer responds differently, has it's own EI needs, dependent upon the lighting. If there are two subjects lit by differing sources correcting/filtering for balance on one, will skew the balance for the other.
It is also quite easy to underexpose one layer just in the shadows while shooting at box speed. This makes for a nasty printing problem.