central stellar densities

I wrote code to measure central stellar densities on SDSS galaxies and tested it on a sample of 1000. I discussed the project briefly with Moustakas, who was reluctant to agree that the lack of red galaxies with low central stellar densities indicates that blue galaxies never quiescently stop forming stars. But I don't see any way around it. I guess the sense in which Moustakas and I agree is that my observation puts a constraint on the gas contents (or sources of gas) of blue galaxies.