Why hasn't my post been posted yet?
Which post?
You posted it to the wrong place. The Themes area is for sharing themes you have made, not requesting that other people make you a theme (which people don't want to have to filter through when looking for themes).
Sorry.
Which section should I post it in?
Help & Support is where questions/requests about Opus should go.
But I'd be surprised if someone makes a theme for you that they didn't already want themselves. 
There are also already some green themes available. Your request of "like the light theme but green" should be satisfied by those, or needs a lot more detail about what you want.
Thank you Jinsight.
I didn't see that in the Themes section!
I'll check it out.