To boost Google search rating, a website needs to have a mobile friendly version.
My guess would be that the green mobile page is a first iteration / trial version, perhaps even automated by a new Web host?
In its current form, it may induce headaches or an epileptic fit and the content it is displaying isn't very useful, but I can see how it could work very well once it has been properly developed.
I'm always zooming in and out and pressing the wrong button on my phone, so I'm pretty sure I'd swap to using the mobile friendly version once it's done.
For now though, I'm glad I found the "desktop" button at the bottom of the page!