Like everything else in PhotoShop, there are dozens of ways to allow part of the color image beneath to show through. By far, the easiest to understand is to simply use the ERASE TOOL. From the TOOLS PALETTE, select the ERASE TOOL. You may need to adjust the size and shape of the eraser, which is done by using the controls at the top of the PhotoShop Screen ~ BRUSH, MODE, OPACITY, FLOW.

When you have a brush that suits your need, begin "ERASING" where you want the color to show through. Simple enough. Proceed to the next slide.