Which is most accurate way to distinguish one of 8 colors?

Question

Imagine we how some basic colors:

RED = Color ((196, 2, 51), \"RED\")
ORANGE = Color ((255, 165, 0), \"ORANGE\")
YELLOW = Color ((255, 205, 0), \"YELLOW\")
GREEN         


        

Answer 1

Short answer: use the Euclidean distance in a device independent color space (source: Color difference article in Wikipedia). Since RGB is device-dependent, you should first map your colors to one of the device-independent color spaces.

I suggest to convert RGB to Lab*. To quote Wikipedia again:

Unlike the RGB and CMYK color models, Lab color is designed to approximate human vision.

Here's a recipe to do the conversion. Once you have the L, a, b values, calculate the Euclidean distance between your color and all the reference colors and choose the closest one.

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Actually, the python-colormath Python module on Google Code (under GPL v3) is capable of converting between many different color spaces and calculates color differences as well.