LAB Coloring it ‘a management technique of colors. It is different from RGB that is additive method based on the three colors red, green and blue, from which its name RGB.
In LAB color instead is a color space-opponent with the size L for brightness, and a and b for color ranges. The Lab color space includes all perceivable colors, which means RGB and CMYK color range.
But how LAB Coloring works?
To work in LAB Color you have to switch the mode from RGB to LAB color
Select Curves into adjustment layers
This time instead of having the range of colors of Red, Blue and Green, as I said at the beginning you will have typical L, A and B color mode
Select A mode and shortens the curve until a new center
Now select B mode and shorten the curve the same, in this case to obtain a new center point you have to move more the curves than the previous step
Now you can adjust the opacity of the layer or mask the result as you want
When edit in LAB Color is finished, merge layers and turn back to RGB mode
To see all the changes and layer intervention step by step