English doesn't give us a good way of distinguishing sensory input from sensations themselves - there's no easy way to distinguish "Light of a certain wavelength is entering my eye" from "I am seeing blue (in a dream or something)." So let me call the former seeing and the latter seezing (the purely subjective experience of seeing).

If you show me a standard American (red) stop sign and I seez this (blue), I may be in some sense wrong about what color the sign is, but not wrong about what I am seezing. In fact, it wouldn't even make sense to be wrong (or right) about what I am seezing.