Thanks for quick answer. But how can use timer interrupt and serial interrupt together? Can you write a short sample code for that?
and what do you think about huge delaying when three leds is being driven by the timer interrupt or main loop. As i said, its 2000Hz with one led.But 60hz with three leds. That's too much i guess.

i have more questions I'm going to send one byte for each led, 30 times in a second.
do you think baud rate is ok for this?

one more i don't know so much about buffer. Can you explain it?