my trees last year were 16' tall, and almost 8' diameter.
I used 100-cnt LED strings, but I folded each back, so each string showed as 50-cnt and 2 strands.
one tree had 8 channels of white, with 3 100s each. and it had 1 channel of 8 greens, and 1 channel of 8 reds.
it was 40 strings of 100, 10 channels.
the other tree had 8 channels of white, with 3 100s each. and it had 1 channel of 8 greens, 1 channel of 8 reds, 1 channel of 8 blues, and 1 channel of 8 pinks.
it was 56 strings of 100, 12 channels.
you can see both in my 2010 videos: WinterLightShow.com
I was able to do tricks with white, and used the colors for accents... I was short on channels and that was my reason not to put the colored strings on separate channels.