Yea, it's very light on any technical details. He did say that the large number of photos allowed him to "increase saturation and contrast". So it sounds like

Yea, it's very light on any technical details. He did say that the large number of photos allowed him to "increase saturation and contrast". So it sounds like e.g. anything showing a hint of blue is interpreted as blue. In a more mathematical sense, a pixel with the RGB value 200,199,203 would be changed to something like 1,0,250. The precise algorithm is more of an artistic choice than scientific, but the general idea is to convert from RGB color space to HSV (hue, saturation, value), increase the "S", then convert back to RGB.