Okay, I really should be getting ready for work, but here is what you can try right now. It should work. It may take a little bit of tweaking here and there, but this should give you a pretty good start. Notice the subtraction node. It is very important to making this work! You will obviously use red for yours. I suggest when opening the color picker, you click directly on the color texture where the red of the shirt shows, so that it chooses the correct shade to remove. Replace the blue with whatever shade you are looking to achieve.