Interactive White Balance Adjustment for Photographic Images
Due to different lighting conditions, white or gray areas in a photograph may not be displayed as neutral white or gray. White balance correction rescales the pixel values in the image in order to make gray areas display correctly.[more]
This Demonstration lets you adjust the white balance of the entire photograph by analyzing a presumed gray pixel in the image and adjusting the remaining pixels proportionally. A pixel with red, green, and blue intensities is assumed to be neutral gray when .
Putting the locator in the original image on top of a pixel converts it in the right image to neutral gray and recalculates the remaining pixels, making the complete image "white balanced."[less]
 Wikipedia. "Color Balance." (Jun 30, 2015) en.wikipedia.org/wiki/Color_balance.