WordPress makes it easy to add an mp3 player to our post and pages, but it can be a bit boring.
You can make the player stand out by tweaking the css.
This is an image of the standard player that comes with WordPress

and here is my modified player
You can use a plugin to set custom css code (I use simple custom css)
/* yellow focus */
.mejs-controls .mejs-button button:focus {
outline: none !important;
}
/*background color*/
.mejs-controls,
.mejs-mediaelement,
.mejs-container {
background: url('') !important;
background-color: red !important;
}
/* text color */
.mejs-currenttime,
.mejs-duration {
color: white !important;
}
.mejs-horizontal-volume-current
{
background:#0073aa!important;
}