try setting outline and/or border properties of select.

select{outline:1px solid green;border:1px solid black;}

Currently there is no way I know of that this can be accomplished using only CSS.

However, using jQuery I was able to achieve a similar effect.

Live Demo

Your dropdown changes because i have to set the size of the select element which makes it look like a list-box. Maybe somebody can improvise on this.

Here is the jQuery i used

$(document).ready(function (event) {   
    $('select').on('mouseenter', 'option', function (e) {
        this.style.background = "limegreen";
    });
    $('select').on('mouseleave', 'option', function (e) {
        this.style.background = "none";
    });
});

Try to change like this, hope it may help you

     select option{
        background: red;
        color: #fff;
        outline:1px solid green;
       }