The author of the contextmenu plugin is more than welcome to take my source and incorporate it into his plugin. It's open source and all. But I having 2 separate plugins will be difficult. The contextmenu author would have to add hooks for menu items, and then I need to be able to hook in there, and get enough information to know which message(s) are being chosen, and then somehow create a UI for picking what to match on and which color to use.
The second feature would be interesting to explore. But im not sure if it's possible to assign labels to specific emails using IMAP.
What I could try to do is find a place for my color labels (I could add a name for each row in my color labels) and use those to filter msgs, so all you see are say 'the red colored images'. Not sure if the current hooks allow me to easily add such filter options