Making a Custom Menu Sidebar Icon show as Current in css [closed]

This isn’t really WordPress specific, but here goes.

Really, all you’re missing is applying the blue background image on .current-menu-item a.

/* Default state base */
.widget_nav_menu .menu li a{
  padding-left: 35px !important;
  background-position: 5% 50%;
  background-repeat: no-repeat;
}

/* Active state base */
.widget_nav_menu .menu .current-menu-item a,
.widget_nav_menu .menu .current-menu-item a,
.widget_nav_menu .menu .current-menu-parent a,
.widget_nav_menu .menu .current-menu-ancestor a {
  background-color: #f3f3f3;
}

/* Power */
.power-icon a {
  background-image: url( /images/icon-grey.png );
}

/* Power active + hover */
.power-icon a:hover,
.power-icon.current-menu-item a,
.power-icon.current-menu-parent a,
.power-icon.current-menu-ancestor a {
  background-image: url( /images/icon-blue.png );
}