use polygonal lasso tool and the magic wand to select the paint then use ctrl+U and check the colorize box and use the sliders to change the colors.... you arent gonna learn over night, it will take weeks to get used to all the tools and even longer to really know how to use them... just practice a lot
If you're just looking to do that use the laso or the magic wand. Yes, it takes a lot, and I do mean a LOT of practice just to get good at it, let alone really good. And to master it? Forget it. I have a degree in Graphic Design and other than the instructions above, I wouldn't know where to tell you to begin. Hmmm. Tutorials in books. Adobe's Classroom in a Book is a good place to start. Take a class. Photoshop, especially when combined with other Adobe products is simply a phenomenal tool. Don't give up, just be patient.