TBH it's been poorly publicised and I think is a bit confusing. It 'looks' a bit like the travel corridors we had last year but isn't the same (AFAIUI).
I expect a lot of people are busy planning/booking holidays without fully understanding it - "Green means go, right?" Most will probably be OK as a lot of places are desperate for tourist income, but there may be some get caught out.
And as happened last year the classifications could change while you're on holiday and you still have to quarantine on return