setColor Mechanic fails on Shulker Mob

Summary Using the setColor skill mechanic does not work on Shulker mob. It will however work on sheep mobs. Also, color option only works if the color is entered in all CAPS.

This happens on Paper/Spigott 16.5 and MM 4.12

Steps to reproduce Create This Mob:

MossMimic:
  Type: SHULKER
  Options:
    Color: GREEN
    Silent: true
    FollowRange: 16
  Skills:
    setColor{color=blue} @self ~onTimer:100 #works on sheep, not working for shulker

Then change the mob type to Sheep instead of Shulker.

Current behavior Trying to get shulkers to change their color based on the block type they are on, like a chameleon but can't get the set color skill to work.

Intended correct behavior Should be able to use setColor in skills and meta skills to modify the shulker's shell color.

Server log file

No errors in log.

Debug log snippet

No messages in debug logs.

Proposed fixes

If can't be fixed, at least the documentation should be changed.