CSS HSLA
/* HSLA (Hue Saturation Lightness Alpha) */
hsl(240, 100%, 50%, 50%)
/* First value: Angle of the color Ciricle */
/* Second Value: Saturation. */
/* Third Value is Lightness. 0% Is black, 100% is white */
/* Fourth value is the Alpha Value */
/* !!! Not tp be mistaken with hsl, which doesn't have the alpha setting */
niconius