Countershading allows for very noticible gradients and changes in the base coat, and therefore all affected genes. As you can see, this goes outside of the range given on the colour guidelines - as long as most of it is at least close to the range and the differing isn't going too far out of range, it is acceptable. It should not come from another colour range other than the base coat, unless affected by artifice.
The exception to this is in monochromatic colonists: White, non-tinted Silver, or Black, or their other-species counterparts. In these cases, the countershading can take on a more saturated colour from one of the other base coat ranges for that species.
It can be compared with a common marking found elsewhere: Pangare.