UncleDrax,
If you want your sweater to be the same color as the package, you will probably have to use about 3 packets of Dye and make sure the sweater sits in an 180 degree dye bath for at least an hour. Even then, it will run in the wash and fade, and the dye itself is not specifically formulated just for cotton. I'm not sure how the sweater will tolerate that heat either.
I would suggest either buying a sweater with the right color

, or using what's called a "reactive dye." The reactive dye is usually called Procion MX and you can dye it in room temperature water, and it will not run anymore after the first couple of washes. Unfortunately, it's something you usually have to get over the internet and costs a little more. It also requires a lot of salt and some soda ash to trigger the chemical reaction.