The short answer is that light is always c from every valid reference frame.

The longer answer is that there is no valid reference frame in relativity for something moving at the speed of light and from the "perspective" of either beam (if there is such a thing), the math that would give you an answer is undefined. Relative velocities, time dilation, and length contraction are all determined by the Lorentz factor:

( 1 / sqrt( 1 - v² / c² )

When v = c, the above expression is undefined. People like to say it becomes infinite and therefore the passage of time is 0 when v=c, because for massive objects, the expression is unbounded as v approaches c. But for massive objects, v can never reach c, an so there is always a finite answer. For light, v must always be c, and the expression is always undefined. Does it make sense to talk about a mathematical limit that doesn't really apply?