Heating cookware with nothing in it for an extended period of time should be avoided, as it can damage the copper coating or warp the pan.
If you somehow avoided warping your pan when you overheated it, the discoloration can easily be fixed.
A greyish dull coating is typically caused by minerals from hard water (if you were boiling water and boiled it dry) getting baked onto the stainless steel finish. The iridescent sheen on the stainless steel finish is due to the finish getting damaged. Luckily both of these can be reversed. The surface of stainless steel is self healing from exposure to heat and oxygen and once you remove the offending finish your cookware will be as good as new.
To repair the finish, first scrub the inside of the pot or pan with a Scotch Brite pad. Note that you should never use a Scotch Brite pad on the outside of your cookware as it will dull the stainless steel shine. As the inside of cookware gets naturally dull from use anyways, using a Scotch Brite pad will not change the already dulled look. After using a Scotch Brite pad, polish the inside of the cookware with Bar Keepers Friend cleaner, which will remove any of the discoloration remaining and help polish the stainless steel.
Overheating a stainless steel pan will not cause any ill health affects. While stainless steel does contain chromium, it is in a form, chromium III, that is harmless and is actually required by the body in trace amounts. The dangerous form of chromium made popular by the film Erin Brockovich is hexavalent chromium, or chromium six, and is unrelated to the chromium used to make stainless steel.
Posted in: Damaged Cookware