Einsteinians readily explain blueshift and redshift when the SOURCE of light is moving - as in the case of sound waves, the motion of the source changes the wavelength so that the speed of the light relative to the observer remains unchanged, Divine Einstein, yes we all believe in relativity, relativity, relativity:
http://www.amazon.com/Brief-History-Time-Stephen-Hawking/dp/0553380168 Stephen Hawking, "A Brief History of Time", Chapter 3: "...we must first understand the Doppler effect. As we have seen, visible light consists of fluctuations, or waves, in the electromagnetic field. The wavelength (or distance from one wave crest to the next) of light is extremely small, ranging from four to seven ten-millionths of a meter. The different wavelengths of light are what the human eye sees as different colors, with the longest wavelengths appearing at the red end of the spectrum and the shortest wavelengths at the blue end. Now imagine a source of light at a constant distance from us, such as a star, emitting waves of light at a constant wavelength. Obviously the wavelength of the waves we receive will be the same as the wavelength at which they are emitted (the gravitational field of the galaxy will not be large enough to have a significant effect). Suppose now that the source starts moving toward us. When the source emits the next wave crest it will be nearer to us, so the distance between wave crests will be smaller than when the star was stationary. This means that the wavelength of the waves we receive is shorter than when the star was stationary. Correspondingly, if the source is moving away from us, the wavelength of the waves we receive will be longer. In the case of light, therefore, means that stars moving away from us will have their spectra shifted toward the red end of the spectrum (red-shifted) and those moving toward us will have their spectra blue-shifted."
The problem is that the motion of the OBSERVER obviously cannot change the wavelength, as in the case of sound waves:
http://faculty.washington.edu/wilkes/116/slides/Physics116_L08-interference.pdf "Sound waves have speed c, and f and L are related by c=Lf. For an observer moving relative to medium with speed u, apparent propagation speed c' will be different: c'=c±u. Wavelength cannot change - it's a constant length in the medium, and same length in moving coordinate system (motion does not change lengths). Observed frequency has to change, to match apparent speed and fixed wavelength: f'=c'/L."
The only reasonable conclusion is that, when the observer moves towards the light source with speed v, the speed of light relative to him is:
c' = f'L = c+v
where f' is the frequency the moving observer measures and L is the wavelength.