Human consciousness tries to form a coherent model that integrates current sensory perception with knowledge. During an approach at night, scarce sensory input is interpolated to form a full model by the brain. The report uses the term "expectation bias" for this phenomenon. This drive for coherence runs below consciousness and we only notice when the coherence falls apart: When our sensory input cannot be reconciled anymore with the current model. We blink, shift our head, and our model rebuilds anew.
What happened here is that the pilots were locked into a wrong model: In an environment with very little light there is no visual source to compare taxiway lighting against. If we know from experience that a light is white, our brain will use this to calibrate. Without this ever becoming a conscious thought. Color correction happens automatically for us and we don't feel it. This process can easily lead to nominally weird things like blue lights being percieved as white.
Fatigue and stress would contribute to ward off looming decoherence such as "why are the lights on 28L redder than on 28R?" When under pressure, we go with the strongest signal. And that signal may very well come from our knowledge, not our perception.