Board Thread:Support Requests - Designing Your Wiki/@comment-46743250-20200922214353/@comment-9605025-20200923005039

On legacy wikis, there is an option to entire a color name or hex code. From your description, it sounds like UCP wikis may have the same option. In that case, have you tried using "transparent"? 8-digit hex codes are a newer thing and are not supported by older browsers.