Color Keying in Blender
A quick look at how to key colors in Blender compositor
Although I primarily use Aftereffects/Photoshop for any color keying work, I had a thought “Can I do this in blender?”
And the answer is: “Yes, you can!” And it is very easy, although not as powerful as the Aftereffects keying algorithm, it still works surprisingly well. You can also combine this technique with a painted alpha mask to have even more control over the results.