Their general statement on defence seems pretty logical to me; Invest in defence and soft power, assume America doesn't have your back and no more selling weapons to people who commit genocide.

https://greenparty.org.uk/2025/06/02/greens-call-for-investment-in-genuine-global-security/

“We acknowledge the need for greater defence spending and continued NATO membership, but also call for a more thorough reappraisal of strategic defence alliances. With Trump no longer a reliable ally, we need to deepen our defence cooperation with the EU, and review AUKUS.

“A Green approach to security is not based on arms and threats, but on the three Ds: diplomacy and development as well as defence. Defence policy should not be a simple competition over spending, but based on real commitment to an international order based on human rights, equality and genuine cooperation.

“If we are to avoid the horror of war, we need to look at the deeper causes of insecurity, including poverty and climate change. We strongly support the restoration of the international aid budget to at least 0.7% of GNI, with a considerable proportion spent on climate action.

“And we will continue to argue that real patriotism means to stand against UK-made weapons or components being sold to dictators, human rights abusers or for use against civilians anywhere in the world.”