Getting this since today's update:

ColouredChat was compiled successfully in 1771ms
[Coloured Chat] Creating a new configuration file
Failed to initialize plugin 'ColouredChat v2.2.7' (NullReferenceException: Object reference not set to an instance of an object) at Oxide.Plugins.ColouredChat.ClearUpData () [0x00011] in <72ac74f2671041eda6b3360a03a5e8b2>:0 at Oxide.Plugins.ColouredChat.Init () [0x0020a] in <72ac74f2671041eda6b3360a03a5e8b2>:0 at Oxide.Plugins.ColouredChat.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x00ab8] in <72ac74f2671041eda6b3360a03a5e8b2>:0 at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <d09a1f46ca2f4432811bcfe45ad13c7b>:0 at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <cf88a28c7fb44d36890d85a78331cc9d>:0 at Oxide.Core.Plugins.CSPlugin.HandleAddedToManager (Oxide.Core.Plugins.PluginManager manager) [0x00043] in <cf88a28c7fb44d36890d85a78331cc9d>:0
Unloaded plugin Coloured Chat v2.2.7 by collect_vood
No previous version to rollback plugin: ColouredChat​

Rolled back to 2.2.3  but same problem:

Failed to initialize plugin 'ColouredChat v2.2.3' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.ColouredChat.ClearUpData () [0x00011] in <acd5fc8bbacc4410b003425f5d7b8834>:0 
  at Oxide.Plugins.ColouredChat.Init () [0x0020a] in <acd5fc8bbacc4410b003425f5d7b8834>:0 
  at Oxide.Plugins.ColouredChat.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x00a6c] in <acd5fc8bbacc4410b003425f5d7b8834>:0 
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <d09a1f46ca2f4432811bcfe45ad13c7b>:0 
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <cf88a28c7fb44d36890d85a78331cc9d>:0 
  at Oxide.Core.Plugins.CSPlugin.HandleAddedToManager (Oxide.Core.Plugins.PluginManager manager) [0x00043] in <cf88a28c7fb44d36890d85a78331cc9d>:0 
Unloaded plugin Coloured Chat v2.2.3 by collect_vood​

Thank you.
Did you data file maybe corrupt? Try to unload the plugin, wipe the data file and load it again.