This tools tracks the color of an area of your image and applies it to a Grade node.
I'm not a Python pro, but I have written a few tools and scripts for Nuke to help me with my day-to-day work. Here you can see some of these tools as well as others that I find useful.
In each entry, you will find the code to copy and use if you want. The codes are Python codes, and the tools are Nuke groups so you can copy the code and directly paste it into your script without needing to install anything.