Untitled

<!DOCTYPE html>
<html>
<head>
    <title>Zaznacz wszystkie</title>
</head>
<body>
    <form>
    <input type="checkbox" id="czarne" >Czarny<br>

     <input type="checkbox" id="zielony" >Zielony<br>

     <input type="checkbox" id="niebieski">Niebieski<br>


    <button type="button" onclick="wybierzALL()">Zaznacz wszystkie</button>

    </form>

    <script type="text/javascript">


        function wybierzALL(){
        if ( document.getElementById("czarne").checked==true && document.getElementById("zielony").checked==true && document.getElementById("niebieski").checked==true){
            document.getElementById("czarne").checked = false;
            document.getElementById("zielony").checked = false;
            document.getElementById("niebieski").checked = false;

        }
        else if ( document.getElementById("czarne").checked==true && document.getElementById("zielony").checked==true && document.getElementById("niebieski").checked==true){
             document.getElementById("czarne").checked = true;
            document.getElementById("zielony").checked = true;
            document.getElementById("niebieski").checked = true;
        }else{
             document.getElementById("czarne").checked = true;
            document.getElementById("zielony").checked = true;
            document.getElementById("niebieski").checked = ;
        }
        }


    </script>


</body>
</html>