How do I convert a red color scheme to a green one without making it look "brighter"
Question
The current color scheme for my desktop uses a red palette. I would like to change it into something green instead so I went through the color scheme configuration file and "rotated" all color values so that RGB becomes BRG. For example, (214,73,55) becomes (55,214,73).
The impression I got was that the green color scheme looked way brighter than the old red color scheme. Apparently this is because we perceive the different colors with different intuitive brightness levels. Is there a formula I can use instead of a simple RGB rotation that will keep the same apparent brightness for the green version of the color scheme? Are there guidelines as to how to best convert a whole set of colors from one base hue to another?
Accepted Answer
Your observation is correct. The lightness (the human perception of brightness) of green is larger than the lightness of red.
In your example, when you shift the sRGB value 214,73,55 to 55,214,73 (i.e. you rotate the hue from 7° to 127°), the brightness remains constant at 84 % but the lightness is increased. The original sRGB value 214,73,55 corresponds to a lightness of 52; the new sRGB value 55,214,73 corresponds to a lightness of 76.
You may want to consider using the CIE L*a*b* colour model (Lab), which is based on the human perception of colour, in order to correct the lightness of the new colour.
Using the Lab model, you may directly reduce the lightness of the new colour to 52, which yields the sRGB value 0,147,0. However, this also increases the saturation of the colour.
Alternatively, you may reduce the brightness of the new colour until a lightness of 52 is obtained, which yields the sRGB value 37,143,49. This ensures that hue and saturation of the colour are preserved.
