Published 27 October, 2008; last updated on 19 March, 2019; originally posted at

I’ve looked for this formula, on average, once a year for the past five or so years. It’s useful for determining what colour text to display over a colour.

Hopefully by posting it here, I’ll be able to find it a bit easier next time.

// r, g and b = the red, green and blue components of a colour
luminance = 0.3r + 0.59g + 0.11b
// if luminance > 0.5, display white; otherwise, display black.