Well, you can do a lot with Green, see ADA's tank's for example.
It just wondered why not use colors more for contrast rather than some pre defined rule.
You will never break into new areas without going against the rules.
Too much red can be a bad thing, but you can explore that and why that is over time, and remove and try a new plant, or allow one to fill in more of an area etc.
This way you learn from your own experiences and still maintain some sense of design and approach. Most do not have 20-30 tanks and managing 10-20 ADA like scapes would be impractical for most hobbyists.
So we can do repeated changes on 1-2 or 3, maybe 4-5 tanks etc, vs trying to do everything all in one block.
Takes longer, but it's more manageable.
Most designs tend to use red are a focal point, but there's a lot of scapes with a good deal of reds. Much more than my tank here.