Top: difference between U − V rest-frame color of the whole host galaxy and local U − V rest-frame color in a region of 3 kpc around the supernova location for SNLS (blue dots), SDSS (red dots), and low-redshift survey (green dots) hosts. The difference is displayed as a function of redshift. The observed redshift dependence (black bins) indicates that the cosmology is affected when local effects are included. Bottom: difference between U − V rest-frame color of the whole host galaxy and local U − V rest-frame color as a function of projected distance to the galactic center in kiloparsec. The color code is the same as for the top plot. The general trend shows that local regions that appear bluer than the host galaxy are located far from the center, whereas locally redder regions are close to the galactic center.