I completely agree with you, though I personally would have provided a list of all 9G available Pokémon with the types they'd ignore (not that I started but I would do it eventually) in the metagame. That subjectivity bothers me too for the writing, yet I wanted to find an original way of using base stats. I'm still looking for other possibilities.
I think you'll have a better chance of getting approved if you come up with something much simpler than the colours.
Like for example that immunities are not based on a single typing anymore but on the dual typing combined. Nothing would change for mono types, but for dual types the new rules are: resist+resist=immune (i.e. appletun is now immune to water and electric), and immune+super effective=neutral (i.e. electric is neutral on gliscor) and immune+neutral=resist (i.e. poison is resist on metagross).
I'm not saying this is a good idea (it probably isn't) but it is much easier to explain and pick up on. Pokémon can be a very complex game already with many rules, adding a lot of extra rules makes it only accessible to the most experienced.