fronend/scss/_multiselect.scss

.ms-container {
    width: auto !important;

    .ms-list {
        @include box-shadow(none !important);
        @include border-radius(0 !important);
    }

    .ms-list.ms-focus {
        @include box-shadow(none !important);
    }

    .ms-selectable,
    .ms-selection {
        min-width: 250px !important;

        li.ms-hover {
            color: #000000 !important;
            background-color: #e6e6e6 !important;
        }

        li.ms-elem-selectable,
        li.ms-elem-selection {
            padding: 9px 15px 6px 15px !important;
        }
    }

    .ms-optgroup-label {
        padding: 5px 0 0 8px !important;
    }
}