Blue

Blue SPD-SL cleats have 2 degrees of float – 1 degree in each direction
Shimano’s newest cleat option – a middle-ground between yellow (SM-SH11) and blue (SM-SH12)
Allows for a small range of movement while still delivering a high amount of pedaling efficiency
Float’s Pivot point is at the front of the cleat, eliminating lateral sliding movement while allowing a small amount of angle change from the pivot point back towards the heel

Yellow

Yellow SPD-SL cleats have 6 Degrees of float – 3 degrees in each direction
Allows for free movement and low joint stress
Float’s pivot point is the center of the cleat, allowing the toes to point in a wide range of angles
The most popular among casual fitness cyclists but are used by a wide range of athletes.
Large float range provides for more room for error when setting up cleats