Adjusting gamma?

So with Nvidia control panel I can do it in windows, what is a good way in linux?

Isn’t that what redshift does?
AFAIK it has different methods available - randr being one of them.

Is there a GUI tool?

Yes there is.

What is a good one?

Perhaps search a bit on your own - or try the things I mentioned.
Only you know what is “good” for you.
Another thing I found when looking for two minutes …
May be available for other DE’s as well.

One can also use the command line tools, create a script and bind it to a key combination - no GUI needed …

If you were using KDE, you can find the gamma adjustment in Systemsettings-hardware-display and monitor-Gamma.

A simple solution , independent of the DE or WM is “xgamma” …
Although is a terminal program , once you know the correct gamma settings you can at it at the startup profile …
Personally I call it whenever I need it via terminal …

I downloaded Gammastep, not sure where it put it. I searched gamma, nothing & menu nothing.

It is a command line program - has no GUI, just an indicator.
It seems to be similar to Redshift.

Being a command line program, there will be no entry for it in your menu.

… it’s not a lot of fun trying to help you because you are always so terse in your questions and replies.
use more words

Oh sorry.

You can install monica from the AUR. It is a bit tricky, the installation will error, but you can follow the instructions in the comments from the link.

Just adjusted gamma with Xgamma. How do I keep the setting through reboots?

Any good gamma adjusting apps (GUI(