Layer Masks

Open an Image in Photoshop

Add an adjustmnet layer to the image

Add a layer mask to your adjustment layer

Use your brush tool (black to remove, white to restore) to show some color back into your image. Select certain focal points to isolate the color on. 

You are going to create at least 6 different designs. Consider each one a grade level with the first 2 getting you to an F, 3 D, etc.