i have sass variable mapped hsl value. when try use hsla add little transparency, doesn't work. i'm doing this: $white:hsl(100, 100%, 100%); .thing{ color:hsla($white,.9); } using gulp-sass build css, error: "required parameter $lightness missing in call function hsla on line {line number} in {file's path}" if replace hsla rgba works fine and, yes, can that, i'd keep colors in hsl. there workaround or sass issue? it's not issue sass, functionality doesn't exist. if @ documentation , there 2 versions of rgba(), 1 accepts of parameters separately , 1 accepts color object. rgba($red, $green, $blue, $alpha) rgba($color, $alpha) if @ documentation hsla(), accepts values separately. hsla($hue, $saturation, $lightness, $alpha) to achieve goal, this: $white:hsl(100, 100%, 100%); .thing{ color: hsla(hue($white), saturation($white), lightness($white), .9); } or... if want pass color object, can create own function since can...