Excess from the fitted red line (X_{outer fit}) vs. magnitude in the Fornax, Virgo, and Coma clusters. As the yellow makers show for FCC301, the excess light drops to zero after putting it at the distance of Coma (the one at the distance of Coma has a “n” “x” symbol on it). A negative (positive) excess is driven by a bluer (redder) center than the galaxy. The very large core sizes are galaxies with extended blue cores.