We've just launched Embed Themes! This has been a very popular feature request so we're very excited to roll this enhancement out :-)
You'll find Embed Themes in Brand section of MyMalcolm. Within each theme you can customise elements like colours, icons and fonts. You then apply your chosen Embed Theme from the Style section of an individual embed (where you can also change some other visual attributes)
As ever let us know your feedback on this feature and other feature requests!