DIAGNOSIS Those are mineral deposits (hard water scale) or protein haze from heating water, especially if you use it for steaming or making stocks. They're harmless but annoying.
FIX Fill the pot with 2 cups of water and 1 cup of white vinegar. Place it back in the cooker base. Use the 'Steam' function for 5 minutes, then let it soak (cool) for an hour. The deposits should wipe away easily. For tougher spots, sprinkle baking soda on a damp sponge and scrub.
IF THAT DIDN'T WORK For persistent rainbow-colored heat tints (which are also harmless), use a stainless steel cleaner like Bar Keepers Friend. Avoid abrasive scouring pads that can scratch the surface.
HEADS UP To prevent this, dry the pot thoroughly after washing. Avoid using the high-heat Sauté function to reduce water to nothing, as that bakes on minerals.