Setting opacity on $primary-color in sass [duplicate]

You can use rgba, i.e.

$primary: rgba(20,20,20, .5);

It works for hex values as well

$primary: rgba(#4B00B5, .3);

You can also set the opacity of colors based on a variable value. For example:

$primary-color: #a61723;
....
color: rgba($primary-color, .5);

Demo