If this happened to me I wouldn't consider the worker to be racist. Then again if a white worker said "Black people your food's ready" I wouldn't consider them to be racist either, however many people would. I find minorities are much less likely to give whites the benefit of the doubt.
Another good example is me and my black friend were shopping at Wal-Mart and he bought a Blue Ray Player and I just had to pick up some deodorant, toothbrush, toothpaste. Anyway when we were leaving the store the white lady at the door saw what he was carrying and asked to see his receipt. After we left my friend was convinced that the lady was a racist because she asked him for his receipt, but didn't ask to see mine.
Now from my own experiences I have been regularly asked to show a receipt leaving Wal-Mart with any item over $100, or a shopping cart full of items and I'm almost never asked when carrying a small bag of cheap items. IMO, she only asked him because what he was carrying was so expensive. Could it have been because of racism, yeah, but chances are just as high, if not higher that race had nothing to do with it. So why automatically assume the woman is a racist? I also wonder if the woman was a minority if his reaction would have been the same.
Another situation. I once asked an Iranian girl out and she said she only dates Iranians. I was like ok cool. We remained friends and I wasn't offended at all. I can understand why someone would only want to date someone within their own ethnic group. I actually felt better about it because she was honest with me and it wasn't because she thought I was ugly or had a bad personality etc. However, I have a friend who's a minority and he always tries to tell me how racist white girls are for not wanting to date him just because he's a minority. To me this is just insane.
The whole dating atmosphere is discriminatory. Some people won't date you because of your hair color, your age, your weight, your height, your religion, political beliefs, etc. People have the right to not take you to bed for whatever reason. It's not racism. It's preference.