>>3189046No, it's not about tone/brightness, but colour.
Generally there are 2 axis on colour contrast: yellow-blue and green-red. With these two axis, you can describe any point in the most crass colour-contrast, snce those two contrasts are the strongest complementary colour-pairs. Making something more yellow also makes it less blue and making something more green makes it less red.
If you take the two most different lights and where they lie on that spectrum, you can create the biggest possible contrast. as I said, in most cases it's yellow-blue. but in
>>3188998 it's red-green because of the red light creating a strong counterpoint to everything else in the picture. some streetlights are also slightly greenish, the one in that picture might be one of those, but I dunno, just a hunch. If it was neutral or a bright blue, it could also have been turned to green via meddling with the contrast. a yellow light would not have created an as-strong contrast, since red and yellow go kind of hand-in-hand.
In pic related you can see the two different contrasts lined up below each other in darktable. you can see, that the original image was leaning way more to the yellow side.
You can also see that histogram-like shadow behind the curve (which at that point isn't a real curve yet). this histogram tells you, that the yellow-blue contrast is much wider and therefore easier to work with. it is also much more even, having similar ammounts of pixels on both sides of the dividing neutral line. red-green has much more weight on the red side. splitting the image along the red-green axis would have created a very evenly red image. and shifting the entire balance more towards green would have denaturized the colours too much
