I am using 2 video sources and I would like to tweak the sky color.
I tried using the highlights setting and the following setting seems quite good to my eye.
R: 0% G: -3% B: -1.5%
I then thought, hey why not calculate the perfect settings.
So switched off the filter, took a screen shot and pasted it into inkscape.
I sampled the more correct looking bit of sky: R:185 G: 205 B: 231
The less correct bit was: R:175 G:225 B:255
I calculated the correction as roughly R: +5.7% G: -8.9% B:-9.5%
I then used those numbers in the filter… way off.
Resulting color is: R:193 G:186 B:209
So I tried R: +2.8 G:-4.5 B:-4.8
Bingo! perfect match. Why are my calcs wrong?