HTML选择选项倍数 - 当不在焦点上时更改所选项目灰色背景

I have HTML select box with multiple selection. When I select item/s and lose focus on the control - the background color of the selected items is gray and I would like to change it to some other color. I can change the background of the selected items but it only works the select box is focused and my goal is to change the color when not on focus. Here is an example in JSFiddle - notice by default the gray background:I have HTML select box with multiple selection.