Green Mode is enabled by default. Retarting game doesn't work, nor does reinstalling.
That's strange, just to be sure, by Green Mode we are talking about this?
If that's the case when opening the game during the BolHut animation at startup, if you hold R and then press L on keyboard, you change the shader. With gamepad it would be the R shoulder and the L shoulder. It's a hidden easter egg.
Something has to be triggering this on startup unintentionally, check for any devices/controllers connected that might be causing this.
I just uploaded a new version of the game for Windows (cannot access Linux right now) where you have to press R+L+A at the same time hopefully it fixes the issue, please download and try it.
That was the very same green mode, however after I restarted my COMPUTER it went back to normal (Only reason I know is I opened it prior to updating it real quick). I would, however, like to thank you for not only the quick response, but also for the fact you pretty much immediately deployed an update in order to fix the issue.