Hello,
Please try to use:
.et-toggle-mob-sidebars-wrapper .et-toggle-mob-sidebar .et_b-icon {
font-size: 20px;
color: #222;
padding-left: 10px;
}
.et-toggle-mob-sidebars-wrapper .et-toggle-mob-sidebar .et_b-icon:hover {
color: white;
}
Regards