What the difference between blue and bleu cheese?

There is no difference between "blue" and "bleu" cheese. They are the same thing!

"Bleu" is the French spelling of "blue". Both terms refer to a type of cheese characterized by its blue-green veins caused by the growth of Penicillium Roqueforti mold.

So, whether you call it "blue cheese" or "bleu cheese," you're referring to the same creamy, pungent, and delicious cheese.