1.) Download the free paint program GIMP at link and install.
2.) Open the image 你 want to paint over
3.) Use the free select tool (it looks like a lasso) to select the area 你 want to paint over.
4.) Once 你 get that selected, pick your color and take the bucket-fill tool. Put it on "Fill whole selection" and click. Keep doing that till you've re-colored everything 你 want colored :D
The way I did it, I took ur picture and I put a picture of Gwen on paint, then I used the color picker and like I took the color of ur hair with the color picker and clothes and stuff and that whole stort and that's how I did it