This happens to mine, and they are most definitely stainless, not aluminum. Our stainless sink gets the same way. I assume it's from all the minerals in our water. I have found that mixing up some Oxyclean and water and a couple of minutes' soak and a scrub with a plastic scrubber will get rid of it (both from the pan and from the sink). It comes right back, though.
I haven't found that it has any negative impact on the usability of the pans, and doesn't shorten the life significantly if the 14+ year old chef's pan I use almost daily is any indication.
I did a little more research, and it's definitely mineral haze. Recommended treatments are Barkeeper's Friend (mild oxalic acid) soak/scrub, or boiling some vinegar, either one followed by a thorough rinse. In theory, if the haze is left alone it could develop into buildup, which would begin to degrade performance, but in practice it's not an urgent worry.
So if it bugs you, clean it off with mild acid or oxygen bleach. But expect it to come right back. If you only removed it once a year, you'd be a couple of years ahead of my cleaning schedule, and I haven't seen any harm from it.
Heat the stainless steal pan on medium-high.
After its hot add your oil.
You'll know your pan is hot enough when the oil has wavy movment when you tilt your pan.
Now raise the temperature gradually until the oil begins become only slighty darker.
If you've reached smoke point you are done (the pan should only be SLIGHTLY smoking)
Remove any excess oil and add new oil.
Cook.
Small amounts of oil are needed for fish without the skin. But if the skin is on and your trying to get it crispy all of the skin on the surface of the fish must be submerged in water to get an effective crust.
Best Answer
The capacity of the pan to store heat is much smaller than for oil or water. Without anything in the pan, the temperature of the pans surface goes up very high quickly. The color change is done by chemical reaction on the surface, thus removal can be done with chemical reagents and/or scrubbing that effected material off the pan.