%, 40%, 60%, 80%) 25 g b / 25%)`, `rgba(25, 102, 153, 0.25)`);
    test_valid_value(`color`, `rgb(from rgb(20%, 40%, 60%, 80%) r 25 b / 25%)`, `rgba(51, 25, 153, 0.25)`);
    test_valid_value(`color`, `rgb(from rgb(20%, 40%, 60%, 80%) r g 25 / 25%)`, `rgba(51, 102, 25, 0.25)`);

    // Testing permutation.
    test_valid_value(`color`, `rgb(from rebeccapurple g b r)`, `rgb(51, 153, 102)`);
    test_valid_value(`color`, `rgb(from rebeccapurple b alpha r / g)`, `rgba(153, 255, 102, 0.2)`);
    test_valid_valu