Help with material settings

Hi guys, absolute noob with materials here.

I’m trying to get this material set up so that the transparent background shows as transparent, the dark green shows as dark green and the white shows as what colour I set it as in the parameter node. As you can see, the dark green doesn’t show up. Ideally, the dark green bit would be black but I tried changing the graphic as I thought that might have been the culprit. I can easily switch it back.

I’ve tried so many permutations, waiting forever for everything to update, trying something else and so on, but I’m tearing my hair out now. Can anyone help me?

Thanks

Edit: I should say: on the texture sample preview, the part in black is actually transparency in the texture.