.tinyMCE-body{
    padding: 5px 20px 5px 20px !important;
    background-color: rgba(0,0,0,0.8) !important;
    color: white;
    font-size: 18px;
}

.tinyMCE-body > p > img, .tinyMCE-body > p > span > iframe {
    max-width: 100%;
    height: auto;
}