No I was talking about over all cast or absortion of spectra.
Think of radio waves....it takes more energy to produce longer wavelengths at a given intensity over distance but they also carry farther and are less affected by objects, trees mountains ect. Shorter wave lengths at a given intensity over distance need even more energy or amplitude behind them to be detected at the same distance than longer wave radiation because they are more easily effected by reflections and multipath interferences...the higher the frequency the shorter the wavelenghth and the higher the energy it takes to propagate over the same distance due to inteference.
It seems to me then that bluer light has shorter wavelengths than redder light and would be more affected than redder light by distance and the particulate/gaseous densities of the space it has to travel to get here. Another words think of a light filter in which only the longer wavelenths at a given intensity get thru more efficiently at a vs. the shorter wavelenths at the same intensity. What can mess up the figures is whether or not there are a larger number of stars producing light at a higher frequency AND very high intensity in a galaxy billions of lightyears distant, these may appear more bluer shifted than others in the same vacinity. Red light to be visible at a certain distance takes more originating energy (due to the longer wavelengths) than blue light at the same distance but bluer light is more effected by the densities of the medium it travels thru than red light would be, so more originating energy would be needed for the blue light source to maintain equal visibility with that of red. For a more practical point...think about a misty foggy night. Red tail lights cut thru better than the yellows and blues. Low beams with its yellower cooler spectra are better to use on a foggy night than brighter bluer whiter light as all that extra light "reflects" back and blinds you with the glare...unless one has one of those million lumen fog lamps often used in "jacklighting" deer(with much higher originating energies therefore higher intensity) that can cut thru the fog by overwhelming its reflectivity.
I'm not saying the blue/red shift tool isn't a useful measure for guaging speed and direction for closer objects, I'm questioning the tools by which we guage the distance and speed of objects farther out than say a thousand light years or so!
I know the scientists extrapolate these equations based on observation of our own sun and planets and derive distances...ect. It is astounding to me that we could figure out that our average distance to our sun was infact 93 million miles even before we sent out probes that would behave exactly as the theoretical equation stated they would...at the exact distances theorectically pre-calculated. So if they say Proxima Centauri is 4.3 light years from us I believe it. I'm having more trouble believing the figures for objects much farther away...especially when it comes to speed and direction!
No need to remain astounded. The information is everywhere. For example: Distances to the Sun and Stars. Words to look up to get you started: parallax, Cepheid variables.
You should check out Encyclopædia Britannica, 1768 edition. It's not illegal; it's not even bigamy; it's trigonometry.
The phenomena you discuss is well known and is taken into account when examining intergalactic distances. Preferential scattering of shorter wavelength (blue) photons is the reason the sky is blue and the setting sun is red/orange. Red shift from stars and galaxies is usually associated with emission spectra of hydrogen, helium, lithium. The shift in these spectra is a Doppler-like effect. The red shift correlates with distances determined using the Cepheid variable stars and supernovae.