Wow, thanks~! The logic gate idea is great! I hadn't thought of that. I didn't mention it, but I also have my own uc in there. I left two pins on the board free for future use. An analog input and a digital output.
I can wire it up with the input from the MP3 status LED to the analog input, and a single transistor on the digital output to drive the additional LEDs. Then it is just software to make it all work.
Here's a neat dual color trick for you. How do you control a dual color LED with a single digital output?
You connect the resister to the LED on the common lead. This wiring only allows one color to light at a time, if both colors are powered the one with the lower forward voltage wins.
Do either a quick experiment or take a quick look at the LED's datasheet to figure out which color to power with the system on and which will be switched on and off.