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HSL is another color definition. Most browsers support it, though only with an absolute alpha channel.
Without an alpha.
background-color: hsl(36,75%,40%)
color: hsl(36,75%,40%)
border-color: hsl(36,75%,40%)
With an absolute alpha.
background-color: hsla(36,75%,40%,0.6)
color: hsla(36,75%,40%,0.6)
border-color: hsla(36,75%,40%,0.6)
With a percentual alpha.
background-color: hsl(36,75%,40%)
color: hsl(36,75%,40%)
border-color: hsl(36,75%,40%)