No, the pan is not necessarily ruined if the area where the ice was fried has changed to a darker color. Stainless steel pans can develop discoloration or "rainbow" marks when exposed to high heat or certain cooking processes. This is known as heat tinting or heat discoloration.
The darkening of the stainless steel surface is usually a cosmetic issue and does not affect the performance or safety of the pan. However, if the discoloration bothers you, you can try the following methods to remove or minimize it:
Stainless steel cleaner: Use a specialized stainless steel cleaner or polish to gently scrub the discolored area. Follow the instructions on the cleaner and use a soft cloth or sponge.
Baking soda paste: Create a paste by mixing baking soda with water. Apply the paste to the discolored area and gently rub it with a soft cloth or sponge. Rinse and dry thoroughly afterward.
Vinegar solution: Make a solution of equal parts water and white vinegar. Apply the solution to the discolored area and let it sit for a few minutes. Scrub gently with a soft cloth or sponge and rinse thoroughly.
Remember to always test these cleaning methods on a small, inconspicuous area of the pan first to ensure they do not cause any adverse effects. Additionally, regular cleaning and maintenance of your stainless steel pan can help prevent or minimize discoloration in the future.