Using variable in rgba is not interpolated correctly

[Raul]

Having a hexadecimal color defined in a variable:

:root {
   --color: #001f3f;
}

and using it with rgba does not give me the expected result:

.style {
    background: rgba(var(--color), .5);
}

The output I get is:

.style {
     background: rgba(#001f3f, .5);
}

[nolimit | DEVELOPERS]

@raulferras solution is combine with https://github.com/postcss/postcss-color-function

[Raul]

Will try, thanks!