All PlayerESP lines are the same color (only on Wurst for MC 1.17.x). The same problem is with MobESP.
Have you checked your settings?
I have restored default settings by deleting wurst directory and options.txt from .minecraft and nothing has changed.
Also, I couldn't reproduce this bug with MobESP. It seems to be working fine:
That's great you fixed it. Thank you. Anyway, I checked MobESP again and actually there isn't any problem with it. Just when I reported the issue, I assumed it was also true for MobESP and when I checked it I did't look closely.