Add secondary color for easy switching

[Marloxo]

Hi @ATBrackeys I would love to help in this project and start by doing this.
If nobody else has worked on this yet, I'd like to work on it and make a PR.

And do you have any specific ideas in your mind for implementing this feature ?

[RamNow]

Hi,
this feature would be great! I would recommend using the right mouse button for the secondary color (like in MS Paint),

Cheers