Change IE background color on unopened, focused select box

Answer 1

Appreciate this is an oldish question, but to prevent the blue background on a selected option in a select dropdown in IE, use the MS pseudo element -ms-value as mentioned by WillRice above. Importantly though you need to set a color css attribute as well for the text as this will get defaulted to white.

select::-ms-value {
    background: none; /* remove blue background on ie10/ie11 when selected*/
    color:#000;
}

More info here