Since the ShiftBrites are in a chain, it's necessary to rewrite all the ShiftBrites when one is changed. So, typically you would make an array[num_shiftbrites,3]. Your output routine just indexes through the whole array, shifts out the values that it finds. Maybe cue that on a timer so it happens automatically. To change the color of one LED, now all you have to do is write new values into the appropriate location in the array.