gentelella/vendors/iCheck/skins/flat/red.css

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

.icheckbox_flat-red {
    background-position: 0 0;
}
    .icheckbox_flat-red.checked {
        background-position: -22px 0;
    }
    .icheckbox_flat-red.disabled {
        background-position: -44px 0;
        cursor: default;
    }
    .icheckbox_flat-red.checked.disabled {
        background-position: -66px 0;
    }

.iradio_flat-red {
    background-position: -88px 0;
}
    .iradio_flat-red.checked {
        background-position: -110px 0;
    }
    .iradio_flat-red.disabled {
        background-position: -132px 0;
        cursor: default;
    }
    .iradio_flat-red.checked.disabled {
        background-position: -154px 0;
    }

/* HiDPI support */
@media (-o-min-device-pixel-ratio: 5/4), (-webkit-min-device-pixel-ratio: 1.25), (min-resolution: 120dpi) {
    .icheckbox_flat-red,
    .iradio_flat-red {
        background-image: url(red@2x.png);
        -webkit-background-size: 176px 22px;
        background-size: 176px 22px;
    }
}