I love the color red, but I don't think u should color ur hair red. Well of course it is ur choice, but I was just giving my opinion, cuz people r beautiful with their natural hair color, and I think dark brown is a very nice color! Any ways,
I think you should blech your hair to lift the color at least somewhat, or else the color will be very dull. How “light” depends on how “bright” you want the red color to be. You will also want to take into consideration the base color of your natural haircolor and watch for color tones that emerge as you lighten the color. This will affect the way you achieve your final color. If all things are agreeable as you finish lightening the color, you can simply add a red color to the bleached hair and get the color you are after.
I STRONGLY recommend that you opt for a professional to do the color for you and that you opt for a red color (which can be more readily camouflaged when you have fulfilled the obligation of the wager) as your choice of haircolor.