How to change a black and whit picture to color?

I screen shot a picture on my iPhone and the pic is in black and white I want to see it in color is there an app that can change it?

No, you collected no color information on the iPhone and there's no way to put the color back in without hand painting it.

You gotta use paint from your laptop

You can't.

In the future, shoot in RGB and then using your computer, process a copy of the original to make it black and white