Hi, 
 
since my monitor upgrade I've encountered a weird issue. The Output color format in the NVIDIA Control Panel is changing from RBG to YCbCr422. This results in colored text which is very unpleasant. It happens out of the blue and constantly after awaking from sleep. 
This seems to be a known issue regarding to Nvidia forums.
  
I would be happy if a EVGA Technician could comment on this issue.  
 
Any help is highly appreciated.
 
 
 EVGA 1080 Ti SC2       Monitor: Iiyama GB3461          Windows 10 Pro           Driver 461.81
 

Yes, used DDU and older driver.
 
Driver is generic which is correct according to support.
Iiyama GB3461 

Updated initial post and new pics.
 
@HeavyHemi 
As you can see I've done a deep research already. Cable is 1.4. 
Others in Nvidia forums bemoan the constantly color format resetting bug. Some threads a 10 years old. 
Out of the blue means unknown trigger. 
The known trigger is restarting from Sleep (Power Options).
Fast Boot is disabled already. 
 
 
 

Unfortunately I've no comparable monitor available. But as you might hinting at I'm quite sure this is a monitor problem. 
The previous monitors had not a single issue. 
 
 

atfrico
May i ask what OS are you using?

Windows 10 Pro

Might be though I don't get why my system should be on the edge. Using a certified cable which did not help.
HDR is disabled, settings are RGB 8bpc. So the native setting 144Hz is overcharging my specs? Is my 1080 Ti too weak?
Besides the color format switches in desktop mode with no load on the system.
 
Changed refresh rate from native 144Hz to 75Hz in desktop mode. RGB seems to stick. Will check this. 

Max Silencio
Might be though I don't get why my system should be on the edge. Using a certified cable which did not help.

Because as you increase resolution, the bandwidth requirement goes up. As you increase the refresh rate, the bandwidth requirement goes up even faster. Features on top of that like 10bpc and HDR require even more bandwidth. YCbCr422 is a compressed color format, it saves on bandwidth. That was my initial clue. 
 
You're literally on the edge of the physical capabilities of the 1.4 official specification. You need Displayport 2.0 for that monitor which offers higher bandwidth, but unfortunately nobody is using it yet. DP 1.4 is equivalent to HBR3 in this chart: https://en.wikipedia.org/wiki/DisplayPort#Resolution_and_refresh_frequency_limits
 
This is why people need to look for (or demand) Disiplayport 2.0 and HDMI 2.1 specs on their GPUs and monitors both. Unfortunately neither your GPU nor your monitor support DP 2.0 or HDMI 2.1. Your specific monitor lists this: (max. 3440 x 1440 @144Hz) for displayport... but that was probably calculated using 8bpc. You tried to use 10bpc which exceeded the bandwidth capabilities of the monitor. 
 
So your setup should work fine if you use 3440x1400 120Hz 10bpc, HDR, sRGB. Should not be any need to go below 120hz unless the monitor or something was having issues.  

Max Silencio
@HeavyHemi @kougar
Thank you for your advice.
So it seems to be irrelevant that my monitors native Refresh rate is 144Hz. Mistakenly I thought changing the rate below the native rate is causing more conversion load. 
 
So the hypothesis is: Refresh rate triggers Output color format as it's limited by bandwidth.  RGB is demanding more bandwidth than YCrCb. If the system is overchallenged it switches from RGB to YCrCb as an easing measure to lessen bandwidth. Is this right?
 
What seems to work is actually lowering the Refresh Rate. I've tested 75Hz successfully about a day and will test 120Hz next. 
 
On the the other hand what contradicts this thesis is:  If the frequency and bandwidth are the trigger of the Color format why is it never changing during heavy gaming? The color format switches exclusively while browsing the internet without videos running. 
 
Here is a typical desktop situation @75Hz and @144Hz: 
 
 

It could be simply that the GPU while running at idle clocks and 144hz is loosing sync with the display. This is one of the reasons why your GPU should be running at a higher idle clock  around 1500mhz when you're running at 144hz for stability.  Running below your native refresh rate actually puts less of a load on the GPU as the pixel clock rate or the data rate is lower.
I suspect this does not occur during gaming because the GPU is operating under a higher voltage. I'm certain that 120hz should work fine for you. It's still possible a better quality cable will work too.

Max Silencio
So the hypothesis is: Refresh rate triggers Output color format as it's limited by bandwidth.  RGB is demanding more bandwidth than YCrCb. If the system is overchallenged it switches from RGB to YCrCb as an easing measure to lessen bandwidth. Is this right?
 

 
That's my theory, yes. 
 

Max Silencio
On the the other hand what contradicts this thesis is:  If the frequency and bandwidth are the trigger of the Color format why is it never changing during heavy gaming? The color format switches exclusively while browsing the internet without videos running. 
 

 
That could be possible with what HeavyHemi was saying. The signal output is generated in the GPU core silicon. In 2D mode it clocks lower and the voltage also decreases... so theoretically it might weaken the driving signal to the point it can't sustain the bandwidth requirements. 
 
Personally I'd just use 120Hz, but that's just me! So if you wish to keep testing this you can test HeavyHemi's theory by adjusting power profiles and/or Precision. Use the sensor tab for GPU-Z to monitor clockspeed and voltages and see how low they go. (Having Precision running activates 3D mode, so keep it closed to let the GPU downclock. It's why I recommend GPU-Z for monitoring). You can also change the NVIDIA driver profile to "prefer maximum performance" and check if that keeps your GPU clock higher.