More heatpipe and fin area. 5x 8mm pipes vs 6x 6mm pipes. Not that more area is the only factor.
FrostyTech tested 4 different color 14PE's and got 0.8c spread.
Red was 14.0c
Silver is 14.8c
Orange = 14.5c
Blue was 14.4c
Guess that mean uncolored is not as good as colored. And red is better than orange and blue.