EDIT: Sorry, I'm not-smart like. You're looking for Liberty 2.0. Hold on, I found that a while back and it's on my phone, I'll just have to search for it again...
The fourth post, by tb110895, contains a link to the stock GB theme for Liberty 1.5 (and, by default, 2.0). It *should* be green & black. If it's not, please let me know.
All Liberty 1.5 themes work with Liberty 2.0, so if there's a different Liberty 1.5 theme you like that you want to use, feel free to use that.
EDIT: I forgot a word of caution. If this breaks Gmail, go into Settings->Applications->Manage Applications->All->Gmail and Clear Data. Detailed in the aforementioned post.