A cooking vessel sidewall cover is provided with an opening therein and a screen is placed over the opening, with the screen including a layered structured between the cover opening and the vessel to include a non-opaque substrate, a layer of thermochromic colorant that changes from a opaque color to a non-opaque color when exposed to a predetermined temperature, and a layer of indicia material which is visible from an outer side of the substrate opening when the thermochromic ink changes to a non-opaque color. The cover may also include protective transparent or translucent window members on either side of the opening, and the substrate may be attached by way of an adhesive.