Setting white balance with gray card

Setting the white balance using the gray card allows you to get perfectly accurate color in different lighting situations. I took several pictures that ones with auto white balance and the others which taken after setting the white balance in the camera(Canon EOS 5D Mark III) using a gray card.

If you see the photos when I put them side by side the difference between the bluer photo before and the warmer photo on the right after setting the custom white balance. Some of the photos can be seen as more yellowish look without customizing white balance and they got more accurate color after customizing the settings. After changing custom white balance, camera had an accurate reference to know what’s a true gray and it shifts the entire color palette to be capturing true color. Some of them you can see the difference at once whereas others you can't.