I have an existing Photoshop file which contains several layers. Each layer is a square shape filled with a solid color. I want to change the color of the squares to Lab values. For example I want one square to be filled with L=50, a=0, b=-20. How do I do this? I am a Photoshop novice.
It depends on how the layers are made :
-> If they are simple pixel layers and look like these :
Choose your LAB color on the color tool :
Then lock the pixels on the selected layer, and use alt/option + delete on the keyboard to fill the pixels with your color. (If you don't lock the pixels, this will fill all the canvas, not only the existing pixels)
-> If they are dynamic layers and look like these :
Simply double clic on the color thumbnail and you'll open the color window.