Originally Posted By: williamani
suprisingly it is a 23f! i tought it would be 24, 25, 26, 27, or 28 but it also can be a 23! but why?
Two options. One, that the ranges are wider than we thought, but the chance of going so far outside the range is very low.

Two, it's already well-known that mutant hair colors (with no apparent relation to either parent) can occur. It can simply be one of these random hair colors, that by random chance, falls close to, but not inside, the expected range.