The Blue Zone is the UN-managed venue where negotiations happen and you need accreditation to enter. The Green Zone is run by the host government and is open to the public.
Almost everything people picture when they think of a COP happens in the Blue Zone: the negotiating rooms, the delegation offices, and the pavilions. A badge is required, and badges come through a government delegation, an admitted observer organisation, the media, or the UN itself.
The Green Zone is the host country’s own programme. At Antalya it occupies the park and the buildings around the tower, and anyone can walk in. In Belém, 700,000 people passed through the Green Zone in the two months before COP30 even opened.