Picture quality

The only way to get 4K on regular antenna TV is if you can receive ATSC 3.0 and you have a local channel that actually broadcasts in that with 4K content. Otherwise TV is just converting it to look as best it can but not being actual 4K originally.

Gemini Air is streaming service only. So depends on the Air itself, your router, internet, and the broadcast's origin (along with all connections in that chain) on what is causing the problem.

Besides just replacing the Air, what other troubleshooting have you tried? Seeing if the issue can be resolved or at least narrowed down to where the problem is starting so further steps could be taken.

There are no over-the-air channels broadcasting 4K video yet. 

What I mean is through my 4k tv my over the air channels have a more colorful picture than the picture that my Gemini Air provides.

Is the HDR and Chroma settings turned on or off on your Gemini Air?

They turned on. I even tried attaching a 4k HDMI cable to the Gemini but it made no difference.

Try resetting your Modem/Router and your Gemini Air at the same time to see if there is any difference.

I just tried it. Still the same duller picture.

I think it has to do with some wierd compatibilty issue's on certain brand TV's. Sometimes my colorspace looks off on the dedicated 4k channels on DTV. It dosent matter if it's thru a Apple tv 4k app or straight from Directv Box to Tv, it's just not as crisp and washed looking most times. If you feed Youtube, not youtube TV it looks great. Go Figure.