The first step is to dig out the pupil with a pen or elliptical tool. Remember to load the pen into the selection. The shortcut key is Ctrl+ ENTER.

Then you click on the picture-adjust-replace color and suck out the color you want to change with a straw. Remember to press the straw with "+". Oh, just click on it, because you think there is no problem in selecting the constituency, and you can pull out the color you want below;

If you don't know how to ask questions, if it helps you, please adopt it.