Yes, but the standard second doesn't depend on wavelength (maybe I should have said "known energy"). You take a Caesium-133 atom, look at it's emission spectrum, isolate the ground state radiation and time a number of oscillations. Of course, the radiation has a specific wavelength/energy, but the calculation doesn't depend on it.
Once you know about time, you can start talking about distance – a meter is defined as the distance light travels in a given time. Given that the meter is defined this way, defining time in terms of speed would be a bit circular.
Once you know about time, you can start talking about distance – a meter is defined as the distance light travels in a given time. Given that the meter is defined this way, defining time in terms of speed would be a bit circular.