Color Replacement tool
Lastly, we have the Color Replacement tool. Like many other tools, this one relies on applying the color change effect to similar-colored pixels. Take a look at this before and after illustration:
This isn't a bad result. I repainted the town hall in the background in a couple of minutes with the Color Replacement tool.
So, if I want to replace blue with red, providing all the blue pixels are the same value, it will work very well – but we all know that life in the digital editing realm is not like this, so that's why we have the Tolerance slider to make Elements be a bit more or less sensitive when it's applying a color change. Increase the tolerance and it will apply the change to lighter and darker shades of blue. You have different brush styles to choose from: four different Blend Modes (I find Color works best) and the inevitable Contiguous or Discontiguous check boxes.