I went into Printemps in Paris and asked about rouille in my best Parisian accent (which used to be pretty good - emphasis on the way-past tense) and the SA looked at me like "pardon?" and I said "um, orange?" and she said "ah!" and brought some out from the back, and I asked her (in French) "what do you call it?" hoping she would pronounce it for me, and she said "orange". Hmph.
I think Atelier Naff has a really good list for some the color swatch seasons that lists the French, Italian and English versions. Apparently Bal actually thinks about this and the translations aren't always exact. For example, everyone says Griege, which is the French, but BalNY says Cement, which is what Bal has designated as the English translation.
My rule of thumb is if I stumble through my request and the SA brings me the bag I want, then I did great! LOL