Dropdown Select Color

Hi, I tried to change the background of the options for the dropdown select, but it doesn’t change. Here’s css code

.wpcf7 select {
	width: 100%;
	padding: 8px;
	border: 1px solid rgba(204,204,204,0.31);
	color: rgba(255,255,255,.9);
	background-color: rgba(250, 250, 250, 0.13);
	border-radius: 3px;
	-webkit-box-sizing: border-box;
	 -moz-box-sizing: border-box;
	      box-sizing: border-box
}

https://wordpress.org/plugins/contact-form-7/