First I'm not trying to go round and round with you. As you state there are more then one way to skin a cat with Photoshop. I do not believe any one way will work every time. Yes I like Eddie method it of course would not work with the gray card or a red wall. I am a little color blind still I can see a difference in the image you masked. Can I tell you which side is gray not without the info pallet, The right side is neutral the left side has more reds then green and blue. The problem I have without the knowledge that the picture is one of a gray card I have no idea that the color was wrong in the first place. All I trying to say is use your head. Methods get tricked if they didn't we would not have to color correct for your cameras auto white balance would get it right every time.. I' sometimes use the threshold method. Sometime just the gray eyedropper in levels. I'll do more then one version If I can not tell which one is better I'll ask my wife to point to the correct one. Where 1 in 10 men are color blind very few woman are. I have good backup...
