Left panel: photospheric activity proxies, S_ph (in ppm), for each of the BLUE, GREEN, and RED channels of the VIRGO/SPM observations as a function of time. Right panel: photospheric activity proxy, S_ph from the VIRGO/SPM GREEN (GREEN dots) and RED (red dots) channels as a function of the photospheric index, S_ph, from the BLUE channel. The solid lines correspond to weighted linear regressions between the data, and the dashed line represents the 1:1 correlation.