Mod Version:
1.12.2-3.4.9.7.
Forge Version:
14.23.2.2613

Link to crash log (if applicable):

Description:
When in desert biome, yellow fog is replaced by blue fog for a milisecond or so.

Several qestions:

• What modpack?
• What other biomes are near by (within 20 blocks)? (If you can get inside the desert where there aren't any other biomes it would be easier.)
• Is it raining, early morning, late evening, etc?

EDIT:

• Any potion effects like night vision or blindness?

EDIT2:

• Does it happen when standing still, or only when moving?

• StatusEffecthud, Ambient Sounds, Dynamic surroundings, Better HUD, SoundFilters
• Can't tell, seed is "-8989846162228293929" without the " - Large biomes
• Midday, no rain.
• No potion
• When moving

To help with the "what biomes are nearby" do you know if you are at the edge of the desert region? Reason I ask is that the logic "averages" the colors of all the biomes in a 20 block square radius around the player position. The flashing is more than likely due to the fact that some of the biomes in that area are reporting "no fog color" for that block column.

EDIT: Another possibility is client side chunk loading. Do your chunks sometimes "pop" into view?

Managed to take a screenshot for a second after bunch of screens. Thats how it looks for a second.

Dont see if its chunk loading.

Ok. Made a test JAR based on some theories. Can you test it out to see if the problem goes away?

EDIT: Another question - looks like you are flying. Is your flight speed normal creative or is it boosted some how? I know it is a strange question but it is relevant. :)

No it wasn't boosted, I also tried it while walking but found it annoying, so reported it.

Cannot seem to replicate it in the jar you've sent

Edit: yup, the new jar fixed it. I still have the issue in the old jar but when I use your new one, its fine.

Cool. This was a good find. :) Fix will be in the next build posted to CurseForge (maybe tomorrow).

Pushed v3.4.9.8 to CurseForge.