The colors between Orange and Green? Yeah that's exciting. I know you can change the color, I even said that I did that on my DX. But the TB only has 3 colors, Red, Green and Orange. HTC went cheap on LEDs.
I just downloaded Handcent again and I don't have any option to change the LED. Only option I have is, Blink LED. On the DX, there was an option for color.
Oh, sorry, you didn't specify LED before, you only said notification, so I thought you were referring to the icon. How many colors do you need for the LED, green & orange seems like it should get the job done. Do you need purple or blue for something? This seems a little nitpicky, or else I'm just not seeing the importance of having several different colored LEDs. If there's a notification light on, you're going to unlock your screen and see what it was and respond accordingly regardless, aren't you?