Probabily, it would be beneficial to first compare gravity, and gravitational waves (GW) as they pass earth's gravitational field.
To compare gravity, and GW, you can consider gravity as a permanent dip in space, while GW is a moving ripple in space.
Wherever this ripple passes, it minutely, and temporarily, changes the shape of the permanent dip. I.e it changes the gravity somewhat (depending upon strength of GW). Then the shape of dip (gravity) would return to its permanent state after the GW has passed.
Therefore, for the impacted time, it should impact speed of light, time, wavelength etc. Because all these get impacted by strength of gravity.
How much - That must have been predicted by general relativity math, may be someone else can quantify that.