This Chat Skin was made for Tundra the IceWing and derives from the Mastery Chat Skin.
Copy the code from MediaWiki:ChatSkin Carribean.css to your CSS page to use this Chat Skin.
Or, you may try adding this experimental import to your page instead;
@import url("/load.php?lang=en&mode=articles&articles=u:heliosanctus:MediaWiki:ChatSkin_Carribean.css&only=styles");