(18:29:35) | Failed to call hook 'OnBetterChat' on plugin 'BetterChatFilter v1.2.2' (InvalidCastException: Specified cast is not valid.)
  at Oxide.Plugins.BetterChatFilter.Filter (System.Collections.Generic.Dictionary`2[TKey,TValue] messageData) [0x00027] in <f2bea8d1e8e2452bb318aaa338aa1fdd>:0 
  at Oxide.Plugins.BetterChatFilter.OnBetterChat (System.Collections.Generic.Dictionary`2[TKey,TValue] messageData) [0x00000] in <f2bea8d1e8e2452bb318aaa338aa1fdd>:0 
  at Oxide.Plugins.BetterChatFilter.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x0004e] in <f2bea8d1e8e2452bb318aaa338aa1fdd>:0 
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <9affce1cd15c4ec183941adef8db1722>:0 
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <4452f821def6406d834e4149849fe7ea>:0 
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <4452f821def6406d834e4149849fe7ea>:0

What version of BetterChat are you using?

5.0.19 i think

You'll need to update else use the previous version of this plugin.

was there a config change?

No, the plugin was changed.

I saw this when I had non-hex colors in the oxide/data/BetterChat.json file.  Change the color names for hex values and you should be ok.

Edit: Also check your other plugin configs to make sure they are using hex, not color names.

A string to another string would not cause this, you would have had to remote quotation marks around something for it to completely change the type and trigger a "InvalidCastException", but pretty sure this error is from using an older version of Better Chat.