Answer:
Custom white balance relies on a gray or white reference point in the scene to accurately capture the colors. When setting a custom white balance, the camera's white balance system is calibrated using a reference point that should be a neutral gray or white color in the scene. The camera uses this reference point to adjust the color temperature of the image and ensure that the colors are accurately reproduced. If the reference point is not a neutral color, the custom white balance may not be accurate, and the colors in the image may appear distorted.