Summary
When you dye a sign that was placed before 1.16.220, it would make the sign text dye bright and illuminated rather than being colored slightly darker.

How to Reproduce
1. Place down some signs and write something in 1.16.200/.210
2. Close and save the world.
3. Open the world in 1.16.220.
4. Dye the sign.

Expected Results
The sign text would be dyed normally but not very bright (or illuminate).

Observed Results
The sign text that was dyed would "glow" like it was dyed together with glow ink sacs.

Notes: I attached a world to test it out. You can work around this issue by simply dye it with ink sacs after the color dye, or break the signs and rewrite the text and later dye it.