As a front-end developer that spend most of his time in CSS I personally don’t see the use of calculated colors and variables. It’s not as if the values are going to change. Example:
.class { color: red + #111; }
…is always going to be interpreted as
.class { color: #880808; }
So just type out the calculated hex value and save your computer a half a millisecond on hexadecimal math.
And as for variables, CSS doesn’t have them because nothing in CSS actually varies. If you have a variable for a certain shade of ‘blue’ then what you actually have is a CONSTANT. And if you want to apply it to a large number of different types of elements then you should focusing on your selectors and inheritances more closely.