Step One
Open the picture that you like to work on. I will use the picture below for this tutorial.
Step Two
Make a new layer and call it lips. Now take any lipstick color that you would prefer for your girlfriend or you. Afterward, using the Brush Tool (B) color the lips of your picture and change the opacity of the layer to anywhere between 10% and 30%.
Step Three
Now we will work on the cheeks. Girls mostly wear pink make up in the cheeks. Therefore, in this case pick the color pink. Then, using the brush tool, color the cheeks. Once you are done that, change the opacity of that layer to anywhere between 10% and 30%.
Step Three
Apply the same effect on upper and lower skin of the eyes and any other part of the faces if needed.
Step Three
This is an extra step. If you want to change the color of eyes, using any selection tool (I will use Elliptical Marquee Tool in this case) make selections around the eyes. Press Ctrl+J to make a copy of the eyes. Now press Ctrl+U and make sure that the colorize box is checked. Play around with the Hue and Saturation Slider for your desire eye color. Below is what I came up with after a little more touch up.
