Idea taken further with simplicity and style in mind.
The thumbnail looks black, but it's actually white
Follow the link and view in full-size...
It is now in .svg (vector) so it's perfectly scalable and it is no font used, lines are drawn. Two choices: this one with the star, or just the two letters. What you think about using this as the 'official' rainbow logo?
Suggestions and examples are welcome..
[edit: added link to text-only version