customize native audio player

Hello,
I have found some css code to change the colors of the nativeaudio player but it seems not working with this theme. Is it normal?

thanks for any help. Antoine

/* WP 3.6 Native Audio Player styling*/

/* change the color of the background */
.mejs-controls,
.mejs-mediaelement,
.mejs-container {
	background: url('') !important;
	background-color: #C8E1FA !important;
}

/* change the color of the lettering */
.mejs-currenttime,
.mejs-duration {
	color: black !important;
}

/* eliminate the yellow border around the play button during playback */
.mejs-controls .mejs-button button:focus {
outline: none !important;
}