Hey SpiderWoman- here. Usually when you color in someone's hair or eyes it doesn't look natural, so I'm going to show you how to make it look natural. The apps I use for these graphics are photoshop mix and photoshop fix, they're both free.

Here are the images we are going to be using.

So the first thing you did is open photoshop mix and put on the black and white filter on the parts that you are changing the color of.

(The hair of the girl on top and the two bottom's eyes)
Once you do that you open your image in photoshop fix. There is an option at the bottom that says paint, once you press on that you choose the color you want for your image.

once you pick the color fill in the area you want colored.

And that's it.