Rubio
 

El brillo de su nuevo rubio a mechas era tan intenso que dolía pensar en cómo lucía antes

Google says
her new blond with locks.

New blond locks would make sense but not this.

I have seen rubio as an adjective for colour or as a noun for a blond person but this suggests rubio as meaning blond hair,

but then, a mechas, with locks, is with a reasonable interpretation?

Blonde highlights, a hair dying technique. :)