What are the core criticisms made by the first wave of green political theory against liberal and socialist theories? Is green political theory modernist or postmodernist?

The point of first wave "green" political theory was to address a gap in both liberal and socialist thinking. While both liberalism and socialism were concerned with social justice and advocated using the power of the state to bring it about, these theories did not take environmental and ecological concerns into account. On a theoretical level, liberals tend to define humans as rational individuals who live in society with each other. Socialists agree with this, but also emphasize the relationship of people to the means of production (a Marxian concept.) "Greens," on the other hand, regard a person's relationship to the environment as the most important aspect of their existence, and the one which needs to inform the politics of their society. "Greens" primarily criticize liberals and socialists for paying insufficient attention to humans as part of an ecosystem.
Whether "greens" are modernists or postmodernists is grounds for debate. In a sense, because they emphasize the relationship of all people, in common, to the environment, they are modernists. There is a universal standard in "green" politics—the health of the planet. However, their calls for a fundamental restructuring of human relations on ecological grounds are postmodernist in that they call much of modernist thinking about nation-states, free markets, and other institutions into question.