I use L'oreal too but I buy it from Sally Beauty supply. The little bottle says what the base color is right on it. May be if you open the box and look at the little bottle it will say on there?
Also, there is usually an 800 number on the box, I know, a pain when your'e standing there in the isle, but I've done it, give it a call and ask the rep before you purchase.
TLHC's one & only PinkyCat
I have a different set of hair goals:
Super long, healthy & curly.
I'm happy to help if I can - feel free to PM me if you're growing long and are stumped.