The blue theme came with TDC2, the initial DC had the yellow theme, which you can still see in the forum review. The blue theme itself though, has changed over the years. If I recall correctly, it had rounded corners at one point too.
TDC had a different Christmas theme also, it had little lights strung across all the title bars, and TDC guy had a candy cane hanging out of his mouth.
I hate yellow/orange. Seems so wierd. TDC should allow you to edit the color, like back in Click Cafe, but I'm not doing it. Shouldn't put some ugly pink default setting like in CC, though, lol.
Disclaimer: Any sarcasm in my posts will not be mentioned as that would ruin the purpose. It is assumed that the reader is intelligent enough to tell the difference between what is sarcasm and what is not.