Night Vision Potion Particles with Different Colors

Do you have any active beacons nearby?

I have one, but the particles I am seeing are either all purple or all blue. And all screenshots were with the same x- and z-coordinates.

Can you please make the same two screenshots, but with your inventory open?

Done.

Ok first of all, the standard particle effect for the night vision potion is blue.
If you have multiple potion effects on you, it's gonna make a mix of the colors.
So my guess is, since you've got 2 active beacons, their maximum effect distance is at that y-coordinate.
Thats why you have a change in particle colors there. Can you deactivate both beacons and check wether the particle color changes then?

The beacon was the problem. I didn't realize they had a vertical radius. Please close.