Why does McCarthy mention Alejandra being pale so many times?

Accompanying the dimming tone is a gradual darkening of McCarthy's imagery. The fist chapter is swathed in morning light. The second unfolds under paper lights, starry skies, in pitch blackness. But the 'darkness' is not meant to be literal - indeed, much of the second chapter reads as idyllically as the first one, only with a contrasting set of hues: She was so pale in the lake she seemed to be burning. Like foxfire in a darkened wood. That burned cold. Like the moon that burned cold. So, I think much of the pale imagery of Alejandra is not only tied up with her pale beauty but it is also infused with the palate of colours that MCcarthy paints so vividly. That's my take!