The presence of a yellow button and its lighting on a microwave can vary depending on the make and model of the microwave oven. In most cases, microwaves have buttons that are either backlit or have a clear plastic overlay to indicate the button's function.
Commonly, microwave ovens have buttons that light up when the oven is in use or when the control panel is activated. This lighting helps users easily identify the buttons and their functions, especially in low-light conditions.
However, the specific colors used for button illumination can differ between models and brands. While yellow is not a typical color used for button illumination, some microwaves may indeed have a yellow-lit button, especially for specific functions like "popcorn" or other pre-set cooking options.
Remember that the appearance and features of microwave ovens can change over time as manufacturers update their designs and technologies. If you are unsure about the lighting or function of a particular button on your microwave, it's always best to consult the microwave's user manual or contact the manufacturer for clarification.