contenido/src/styles/blockquote.css

Contenido is a library with a set of tools to help you create your own rich text editor on top of draft-js without thinking about how to handle things.

.blockquote > .public-DraftStyleDefault-ltr {
  padding: 0.5rem 0.75rem;
  border-left: 4px solid rgba(125, 125, 125, 0.5);
}

.blockquote > .public-DraftStyleDefault-rtl {
  padding: 0.5rem 0.75rem;
  border-right: 4px solid rgba(125, 125, 125, 0.5);
}