OpenSea is having issues right now showing avatars on many names. There’s a separate post about what’s going on here: OpenSea "content not available yet" and missing ENS names
If you were to refresh the metadata on the older colorful backgrounds, it will show the new blue background. The ENS names that have these older colors is something OS generated I think, and they update to the new standard blue on a metadata refresh. However, that might be up in the air if OS is still having trouble showing the content.