Modify alpha opacity of LESS variable

Question

Using LESS, I know that I can change the saturation or tint of a color variable. That looks like this:

background: lighten(@blue, 20%); 

I want to change the alpha opacity of my color, though. Preferably like this:

background: alpha(@blue, 20%); 

Is there a simple way to do this in LESS?

Answer 1

The site documentation gives the answer:

background: fade(@blue, 20%); 

The function name is fade not alpha according to that document.