No artifacts so far, thank you. However when I put my laptop to sleep at deep night (1900K) and wake it up another day, I need to restart f.lux. It shows 6500K, however 1900K temperature is still applied. Closing f.lux does not fix it, I need to run it again. Not a big deal though. 4.118

Here's also a thread about red ones: https://forum.justgetflux.com/topic/7279/red-screen-artifacts-when-flux-is-on

If it doesn't do it by itself you can rightclick on the icon in systray, go to "about flux"
Check the "join f.lux beta ..." box and close the about dialog. Then, the auto-update should work.
After that, you can uncheck the box in "about flux" again.

Edit: Direct link: https://justgetflux.com/flux-setup4-115.exe

If you want to uninstall it completely, you can go to Settings -- Apps and features -- f.lux -- Deinstall/Remove

One thing I want to say: I'm not 100% sure but I think that I didn't expand the color range after this update - but it was expanded in the prior win update 1909..
Maybe it expanded itself by running with admin permissions? I don't know but I also don't care. The artefacts are gone and that's the main thing!

Sorry if I wrote something wrong I just Russian and wrote everything through a translator.

Usually, if this one-pixel test fails, it means that it just didn't work at all - Windows is saying "no", and so we assume nothing has visibly changed. In this case, it seems to work sometimes (maybe on a second monitor) but it returns an error saying it didn't. So f.lux was not "fixing" the test because the test said it didn't work. (The update fixes it always now.)

What took me so long: I'm expecting that most of the people on this thread didn't click the "expand color range" prompt when Windows updated. And my machine had this set, so I didn't test that case. But it was the important one to test.

Will be posting a beta in a bit.

1. I tried 446.14, 441.87, 445.98 and 430.53 as I wrote before and it appeared everywhere
2. The gray color #818586 (R129 G133 B134) gets blue. See the image in my post before
3. First one with DVI, second with displayport. But I already tried both display port, one DP and one HDMI, one DVI and one DP. Affected is always the hardware based second monitor, like seen in Settings -- System -- Display
4. I have a Inno3D iChill GTX 1070 X3. According to their website it supports Dual Link DVI-D, HDMI 2.0b, 3x DisplayPort 1.4
5. Haswell i5 Processor 4460, Chipset B85 - i don't think it's a "newer one with onboard color" :)

Advanced Micro Devices, Inc. 15.301.1901.0: AMD Radeon HD 5700 Series (20160226)

ViewSonic VX2250 SERIES, 477 x 268mm, built 2011
Chromaticities:
R=0.641602 0.344727
G=0.320313 0.589844
B=0.159180 0.077148
W=0.313477 0.329102
sRGB gamut: 85%, AdobeRGB gamut: 57%

Generic PnP Monitor, 477 x 268mm, built 2011
Chromaticities:
R=0.634766 0.348633
G=0.332031 0.609375
B=0.155273 0.054688
W=0.312500 0.329102
sRGB gamut: 76%, AdobeRGB gamut: 54%

Monitor 1 on AMD Radeon HD 5700 Series: VCGT=0 gamma=1
Monitor 2 on AMD Radeon HD 5700 Series: VCGT=0 gamma=1

Windows Build: 19041.329

NVIDIA 26.21.14.4614: NVIDIA GeForce GTX 1080 (20200515)
Citrix Systems Inc. 12.40.44.247: Citrix Indirect Display Adapter (20190123)

Dell U2312HM (Digital - DisplayPort), 510 x 287mm, built 2013
Chromaticities: 
  R=0.637695 0.330078
  G=0.311523 0.623047
  B=0.150391 0.068359
  W=0.313477 0.329102
  sRGB gamut: 99%, AdobeRGB gamut: 68%

Dell U2312HM (Digital - DisplayPort), 510 x 287mm, built 2013
Chromaticities: 
  R=0.639648 0.333008
  G=0.311523 0.625977
  B=0.153320 0.070313
  W=0.313477 0.329102
  sRGB gamut: 99%, AdobeRGB gamut: 69%

Monitor 1 on NVIDIA GeForce GTX 1080: VCGT=0 gamma=1
Monitor 2 on NVIDIA GeForce GTX 1080: VCGT=0 gamma=1

Windows Build: 19041.329

Ignore the Citrix display adapter; I have some Citrix software installed for work but it's not a real device.

@herf said in Windows 10 May 2020 (2004) Update - Blue/Green Squiggly Lines on Secondary:

Well, I am stumped so far. We usually find it easier to track these bugs down, so here are some more questions!

On a test machine here, I have an NVIDIA GTX 1050Ti with 446.x installed. The machine has Haswell (4th-generation) CPU. I have two displays connected only to the NVIDIA GPU on DisplayPort and DVI-I. The HDMI connector is not used. Perhaps a newer CPU would be needed, or HDMI or another kind of interface?

Some questions:

1. Is everyone who's seeing this bug on NVIDIA right now? 446 drivers?
2. What content exactly is giving the problem?
3. How are your monitors connected?
4. Which version of displayport or HDMI do your GPUs support? My GPU is older and so supports DisplayPort 1.4 and HDMI 2.0. Some newer cards support the HDR-capable HDMI 2.0a/b, which is one thing I'm wondering about.
5. Which Intel "generation" do you have? Some of the newer ones have on-board color support.

Thanks!

To answer your questions:

1. Yes, latest production drives (446.14).
2. I've noticed this problem pretty much exclusively with Youtube content no matter the browser (Firefox is my primary, but I've seen it in both Chrome and Edgium).
3. DisplayPort.
4. DP 1.43, HDMI 2.0b, DL-DVI.
5. Haswell generation i7-4770K for me. Chipset is Z97 on an MSI Z97A Gaming 7 motherboard.