Plugins have direct access to the DOM and thus a great deal of flexibility in how they are styled. Some conventions have emerged.
Text in Paragraphs or other paragraph like items renders black on white, san-serif, full width paragraphs.
Computations or other interactions with systems and services are rendered in in light gray boxes often with markup commands echoed as labeling.
<div style="background-color:#eee; padding:15px; margin-block-start:1em; margin-block-end:1em;">
Status is shown smaller, gray and centered.
Buttons are shown centered, disabled and labeled "wait" until bound and activated.