Lorna Slater and her co-leader Patrick Harvie have been in informal talks with the SNP, which are now moving to a formal basis.
First Minister Nicola Sturgeon said the talks could lead to a formal co-operation agreement between the parties, and possibly Green MSPs becoming ministers.
Ms Slater told BBC Scotland’s The Sunday Show: “I wouldn’t use that word [coalition] at all.
“Green parties around the world have different co-operation arrangements with governments and it doesn’t at all mean a coalition.
“It could just be co-operation in specific areas – for example, tackling the climate crisis while still being in opposition in other areas.
“We just don’t know what kind of model will work for Scotland yet, all we’ve done is say we will look at the models available.”
Ms Slater said she was “a little bit surprised” to be approached by the SNP about working together.
She said: “It represents a new kind of politics, a different way of doing things where we work across party to tackle the big issues.
“It was something we talked about in hustings … I guess I’m both surprised and delighted that the government has followed up on that.”
Questioned if she herself would like a ministerial office, Ms Slater said she has only been an MSP for three weeks, before adding: “We can work up to it.”
The Scottish Conservative spokesman for energy and net zero, Liam Kerr, said: “By whatever name the SNP and Greens will call it, this coalition stands to jeopardise the North Sea energy industry’s future.”
He added: “An alliance with the Greens will drag the Scottish Government further and further away from protecting jobs and the needs of our economy on to their pet projects and impractical policies.
“The SNP need to abandon this crazy plan and put the interests of all of Scotland before the interests of the nationalism movement.”
Former SNP MSP Alex Neil, who served in both Alex Salmond and Ms Sturgeon’s governments, has urged the First Minister to be cautious in the coming negotiations.