Conventions for Video and Audio RSS Feed Icons?

I just came across three versions of the RSS icon on the Stargate Worlds web site. I’ve not seen green or blue icons being used to represent video and audio RSS feeds before.

I was wondering if this was a convention I wasn’t aware of or if this was just how they were trying to differentiate the feeds on this web site.

If the second option is true, I’m not how well it works as the only way to know what the blue and green RSS icons represent is to mouse over them. This doesn’t make them particularly ‘discoverable.’

Anyone have any ideas?