The plugin has hex colour support through both holograms and plugin messages.

In game holograms:

<#e7f10a>my text</#e7f10a>



Config:
In the config you can put hex colours anywhere like this:

Reflected in game like this



Both config and holograms support gradients and rainbows too.
E.g
<#FF0000>Message</#00FF00>

Holograms support all available colours and options as present in DecentHolograms

Yes. The plugin supports most features built into DecentHolograms

For example, a spider entity hologram can be made by inputting #ENTITY: SPIDER into the anvil GUI


Heads can be made too by inputting
#HEAD: PLAYER_HEAD (YourPlayerName)


Items, animations, hex and more are all supported and can be found by exploring the DecentHolograms documentation