#404040

The closest CSS color name to this value is "darkslategray", which is not the same color. Everything below is arithmetic on the value itself.

HEX

#404040

RGB

64, 64, 64

HSL

0, 0%, 25%

Closest CSS name

darkslategray (not exact)

Contrast with white

10.37:1

Contrast with black

2.03:1

Reading the contrast figures

Those two ratios are WCAG 2.1 contrast, measured between this color and plain white or plain black. They are the numbers that decide whether text of that color would be readable on this background: 4.5:1 is the threshold for normal text under success criterion 1.4.3, and 3:1 for large text. A ratio is one fact about a pair of colors, not a verdict on whether a design is accessible.

Other colors

Sixteen colors have pages like this one: the values this site already uses in its own tools. The Color Picker shows any other shade full screen and puts it in the address, so you can share it without a page ever being created for it. The Color Converter writes a value three ways, and the Contrast Checker measures any pair rather than only black and white.