I've got the blue 1.25 - it plays slightly crisper than the yellow. The difference is only minor but if you use these strings alot, you do notice a very slight difference.1.25 is 16L for Yonex. I have a similar issue with PTP 1.25. The 1.20 (17) plays better for me in terms of launch angle and general playability. I have only played yellow. I have read black and blue play slightly different.