fronend/scss/_dropzone.scss

.dropzone {
    border: 2px solid transparent !important;
    background-color: #eee !important;

    .dz-message {
        .drag-icon-cph {
            .material-icons {
                font-size: 80px;
                color: #777;
            }
        }
    }
}

.dz-drag-hover {
    border: 2px dashed #888 !important;
}