There is a kinda secret, yet well supported CSS feature called currentColor. It's like a special CSS variable that has been supported in almost all browsers for almost all time (see linked Caniuse).

Usage

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The currentColor value can be used in CSS to indicate the current value of color should be used. A common use case is setting a border color:

a.ghost
  color: white
  border: 1px solid currentColor
  &:hover
    color: red // Border color will change as well 

Note that in many cases, you can simply omit the color to achieve the same result (i.e. in the example, simply write border: 1px solid).