Blue (481 nm) over orange (649 nm) or red (701 nm) color ratios of the evolving region on 18 June 2015 (upper row), 2 July 2015 (middle row), and 11 July 2015 (lower row). The first column shows a context image of the region, the second column shows the color ratio (blue-to-orange for 18 June and 2 July, blue-to-red for 11 July), and the third column shows a color-composite image made of the first two columns. The yellow arrows indicate where features A, D, and E started (Fig. 1), with a material bluer than average (value above 1 in the color ratio). The images were acquired with the NAC.