First panel: Comparison of the rotation period vs. B–V for Log = −5.1 from various sources: the solid black line is from Mamajek & Hillenbrand (2008), the green dot-dashed line from Noyes et al. (1984a), and the dashed red line from Saar & Brandenburg (1999). Second panel: Same for Log = −4.75. Third panel: Similar comparison vs. Log for eight levels in B–V between 0.5 and 1.1. The vertical line approximately shows the lower limit for the validity of the laws (the shaded area indicates the zones where it is not valid).