Similar Color Shades codes

If I see a particul开发者_开发知识库ar shade of red on a website, how do I find out what the same shade will be in a different color? Example in Green or such?

To see the same shade (saturation and brilliance) in different hues, convert the color to HSV or HSB, and then increment/decrement the Hue value.

This web page describes how to convert RGB to HSV, and even includes sample C code.

http://en.literateprograms.org/RGB_to_HSV_color_space_conversion_%28C%29

...Though you might find more useful algorithms/snippets on the web.

http://www.google.com/search?q=Convert+RGB+to+HSV