mlang38

This plugin seems to style the message using these CSS classes :

.juiz-outdated-message {
        margin: 1em 0;
        padding: 10px 15px;
        background: #FFF;
        color: #666;
        line-height: 1.4;
        font-size: 1em;
        box-shadow: 1px 1px 4px rgba(0,0,0,.1);
}

// Custom style for message above the post content
.jodpm-top {}

// Custom style for message below the post content
.jodpm-bottom {}

You could customize this wether with a child theme style.css or with a “Custom CSS” plugin, I think.