How do you change the border color of iCheck checkbox to match its surrounding color?

Question

There are still white borders that can be seen with icheck. Is there any way to make this disappear? I've tried all sorts of things like change the background and border color of the div it's in and what not but it absolutely has no effect.

<td>
 {!! Form::checkbox('checkbox_to_approve', '1', null, ['id' => 'checkbox_to_approve_' . $index, 'class' => 'checkbox_to_approve', 'disabled' => 'disabled', 'data-work_day_id' => $time_record['work_day_id']]) !!}
 {{Carbon\Carbon::parse($time_record['work_day'])->format('m/d')}}
</td>

$('input[id^=checkbox]').iCheck({
    checkboxClass: 'icheckbox_flat-naviblue',
    radioClass: 'iradio_flat-naviblue'
});

.icheckbox_flat-naviblue,
.iradio_flat-naviblue {
    display: inline-block;
    *display: inline;
    vertical-align: middle;
    margin: 0;
    padding: 0;
    width: 20px;
    height: 20px;
    background: url(naviblue.png) no-repeat;
    border: none;
    cursor: pointer;
}