i am new to the blackberry scene but as far as I am aware, only the 8100 had a led lit trackball. all the other pearls have a white led lighting the ball. Other than that, i dont even know how you would go about changing out the trackball/led, I have never seen the circuit board in this phone and i dont think i ever will.
8130 you cannot change the led under the ball you can color it with a marker, but you can change the blinking LEDS. one app for that is called missinglight which changes the missed call light to a purple light but if i remember correct the colorball app also changes the blinking leds for the 8130