When I started, I was trying to recreate the old UI. That turned out to be a technical nightmare. So, I scrapped my work. I restarted from scratch and kept the old UI in mind. I didn't set out to make it exactly like the old UI. I just wanted it to resemble it.
In the beginning the marble color was blue. I decided to change it grey so that ppl can change the windows to any color by right clicking them and playing with the rgb tint values. (even though every thing won't change color; It still looks semi-ok because, grey matches everything) Plus, I like grey. It's easy on the eyes. The only black backgrounds are the titlebars. The chat windows can be lightened by raising the tint values from 127.
I know it can look a lot nicer. I'm not the most artistic guy around.
Edit: Removed the last comment since it is no longer true
