Every exposure is 18 bits per pixel, each channel is a separate exposure. So a full image of one patch of the sky would be either 5 or 6 individual exposures for each color channel (plus a clear exposure) which would be equivalent to 90 or 108 bits per pixel.

There isn't a 1:1 match of filter channels to RGB colors but for just the 3 color channels closest to RGB that would be the equivalent of 54 bits per pixel, or 18 quadrillion colors.