Please put style rules in chrome://magnifier/skin/ Puntuado con 4 de 5 estrellas
Please put style rules in chrome://magnifier/skin/magnifier.css.
The style rules directly applied to the content cannot be easily overridden by a theme.
I think there is actually no need for that. I use all the devtools classes to style the panel. I will try to move a little remaining things to css in next update.