Detect similar colours from hex values

Question

Does anyone know of a way of taking two hex colour values and returning some kind of index to say how similar the colours are? e.g two shades of yellow might return a higher ind

Answer 1

I've been searching Pascal code for a solution.

I dropped the Pascal restriction and found this question.

The Red(), Green() and Blue() functions replace the "parseInt"s.

Result:=(R/255+G/255+B/255)/3

replaced

r /= 255;
g /= 255;
b /= 255;
return (r + g + b) / 3;

Bazza