Environmental conservation is green, representing ecocentricity, first priority to the Earth. Sustainability is pinkish-brown, representing anthropocentrism, first priority to humans. Sustainable action aims to create efficient societies which prosper against the odds of diminishing resources. Sustainability appears ecological, but is human-centered. But that doesn't have to be a bad thing. Just don't call solar panels green because photovoltaic cells are not trees.
Humans cannot live when the sky is black and the soil toxic, so environmentalists protect Gaia's resources; but is society's faux-environmentalism equivalent to ecocentricity? Perhaps there is more self-interest at stake than the green movement would have one believe.
Societies alter nature to fit their needs. This is apparent in the Netherlands. The Dutch have historically bent nature over backwards to serve their demands. Have you ever been passed by a boat that is sailing meters over your head, while dry? A most unnatural feeling, yet the Dutch were able to pump their land dry(ish) and keep gravity, potential energy, and all the fish locked behind a dike.
What is after green? We are. For sustainable societies of greater population to prosper, nature will be increasingly rerouted to cater for anthropocentrism. Unnatural land will be formed against a rising ocean. Unnatural genetically modified plants will feed more mouths. Unnatural deserts will be solar farms. Unnatural algae will grow jet fuel. Unnatural bacterial will build plastic. Propagating society's further ascension will not be green. Mid-city skyscraper vertical farming is not natural, is not green, but it is sustainable.
Radical conservationists would direct humanity towards a simpler time, to small-is-beautiful society, to ecocentricity. Why slow down the color, the creativity, and the spectacle? Humans are the most interesting, beautiful, and dynamic life this planet has to offer. Like all rules, the natural laws of the universe (gravity, inertia, entropy &c) were meant to be broken. Straighten the rivers, extend land into water, grow sustainable cities, and colonize mars. Long live humanity!