This color scheme is probably about the most useless feature of OrangeCD

Green color corresponds to simple data tags.

Blue color corresponds to clickable links. The start and end tags will produce <A HREF="something"> and </A>.

Yellow color is reserved for any tags that produce multiple values. For example, it's used for tags that enumerate tracks or artists. For example, <dax:track>...</dax:track> will reproduce the content between start and end tag as many times as there are tracks on the album.

I hope this helps!

Andrei