 40%, 60%, 80%) r 20% 10)`, `rgba(51, 51, 10, 0.8)`);
    test_valid_value(`color`, `rgb(from rgb(20%, 40%, 60%, 80%) r 10 20%)`, `rgba(51, 10, 51, 0.8)`);
    test_valid_value(`color`, `rgb(from rgb(20%, 40%, 60%, 80%) 0% 10 10)`, `rgba(0, 10, 10, 0.8)`);

        // r    g    b
        // 102  51   153
        // 40%  20%  60%)
    // Testing with calc().
    test_valid_value(`color`, `rgb(from rebeccapurple calc(r) calc(g) calc(b))`, `rgb(102, 51, 153)`);
    test_valid_value(`color`, `rgb(from rebeccapu