The bug
The mere existence of this orange colouring in the visibility of block/sky light in general is nonsensical, since everything is meant to be fully lit with the effect. This is caused by dim lighting either from blocks that are distant from the light source or by low brightness settings. This is much more noticeable with the Lighting set to "Moody", but it occurs in all settings.
The code analysis in MC-58177 may apply here.
To reproduce
Give yourself Night Vision.
Go in a cave and find some flowing lava.
Notice that the blocks about seven blocks away have an orange tinge and are darker than they should.
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Hi there!
I can confirm.

Can confirm as well! 1.16.2
Can confirm for release 1.16.3! Does not work if brightness is set to Bright; works best with brightness set to Moody.
Here are some steps to reproduce this issue:
Steps to Reproduce:
Change your brightness level to moody. (
Options > Video Settings > Brightness: Moody
)Enter a dark place. (Cave)
Place down a light source.
Give yourself night vision.
/effect give @s minecraft:night_vision
→ ❌ Notice how the light appears darker and orange.
Can confirm in 21w08b. Video attached.
Can confirm in 1.16.5 and 21w10a.
Can confirm in 21w16a.

this affects 1.18 and 1.18.1! i think or its a different bug
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Can confirm in 1.18.2.
Can confirm in 1.19 and 22w24a.
Can confirm in 1.19.2.