Temporary bluing/discoloration may occur but it is normal and very easy to remove. It’s a food film residue caused by high heat, oil and trace minerals in the food you are cooking. It appears cloudy on stainless steel but more colorful on NanoBond due to the mirror-like impenetrable surface. You can restore the titanium brilliance every time with a little stainless steel cleaner like Hestan Professional Cleaner and a Scotch-Brite pad. The surface is so resilient, even tough stains like polymerized oil or high heat oxidation can be clean like new, dish after dish.