Modifying Color through Curves

I found the lesson Multi-Mask Operations as especially useful lesson. Although you did not cover this topic in that lesson, when I examined the masks in your image I found a mask called Cement color that was attached to a curves adjustment layer in which you changed the color of the light blue cement to match the color of the cement in the image. Actually you got the cement color to look uniform–the color wasn’t an exact match because it was really brighter. After trying to emulate your curves adjustment layer unsuccessfully, I would like to see a lesson on using curves to modify colors.