Features

With this plugin, shulkers can be dyed by interacting with them while holding any dye. Shulkers cannot be undyed on 1.13+ servers because I'm not sure how this mechanic should work. (If you have an idea, you can let me know by opening a GitHub issue proposing your idea.)

Dyeing a shulker requires the dyeableshulkers.dye permission.

On 1.15.2+ servers, the player will swing their hand upon dyeing a shulker. This can be disabled on a per-player basis by revoking the dyeableshulkers.dye.swing permission.

On 1.17+ servers, the item.dye.use sound will play upon dyeing a shulker. This can be disabled on a per-player basis by revoking the dyeableshulkers.dye.sound permission.

API

The plugin calls io.github.maninmyvan.dyeableshulkers.event.ShulkerDyeEvent when a player successfully dyes a shulker. This event is cancellable.
The shulker that was dyed can be obtained with event.getShulker(), and the player that dyed the shulker with event.getPlayer(). The color that the shulker will be set to can be obtained with event.getColor() and changed with event.setColor(color).