Hey Manu, you can already do that
Just go in TableScan to Configure > Player Notes and import your notes file to show all the colors in TableScan. And as I said in the future you will be able to automatically assign fish icons or other labels based on a player's note color.
Edit: After rereading your post I see that you already knew that and you just want to filter by note color, sorry for the misunderstanding and yes that is also something I'll consider, although with my current idea, if you can make a green player a whale, then you could of course just filter for whales, so how would you use the filters for note colors differently?