 alpha)`, `rgba(51, 25, 153, 0.8)`);
    test_valid_value(`color`, `rgb(from rgb(20%, 40%, 60%, 80%) r g 25 / alpha)`, `rgba(51, 102, 25, 0.8)`);
    test_valid_value(`color`, `rgb(from rgb(20%, 40%, 60%, 80%) r g b / .20)`, `rgba(51, 102, 153, 0.2)`);

    // Testing replacement with a percentage.
    test_valid_value(`color`, `rgb(from rebeccapurple 20% g b / alpha)`, `rgb(51, 51, 153)`);
    test_valid_value(`color`, `rgb(from rebeccapurple r 20% b / alpha)`, `rgb(102, 51, 153)`);
    test_valid_value(`c