# Test Color Contrast

## Color Brightness Formula

The following is the formula suggested by the World Wide Web Consortium (W3C) to determine the brightness of a color.

((Red value X 299) + (Green value X 587) + (Blue value X 114)) / 1000

The difference between the background brightness, and the foreground brightness should be greater than 125.

## Color Difference Formula

The following is the formula suggested by the W3C to determine the difference between two colors.

(maximum (Red value 1, Red value 2) - minimum (Red value 1, Red value 2)) + (maximum (Green value 1, Green value 2) - minimum (Green value 1, Green value 2)) + (maximum (Blue value 1, Blue value 2) - minimum (Blue value 1, Blue value 2))

The difference between the background color and the foreground color should be greater than 500.

## Luminosity Contrast Ratio Formula

WCAG 2.0 Guideline 1.4: Make it easy to distinguish foreground information from background images or sounds.

(L1+.05) / (L2+.05) where L is luminosity and is defined as .2126*R + .7152*G + .0722B using linearized R, G, and B values. Linearized R (for example) = (R/FS)^2.2 where FS is full scale value (255 for 8 bit color channels). L1 is the higher value (of text or background) and L2 is the lower value.

Text or diagrams, and their background, must have a luminosity contrast ratio of at least 5:1. (Level 2)