Font, Size, Colour

Don’t edit custom.css.

The plugin does not provide settings for that yet.

There are several options for custom CSS.
http://www.wpbeginner.com/plugins/how-to-easily-add-custom-css-to-your-wordpress-site/

1. Your theme’s stylesheet. Not recommended if you are using a free/premium theme as the next theme update will overwrite your modifications.
2. Your theme’s custom CSS section if it offers one.
3. The Additional CSS section of the Customizer.
4. A plugin like Simple Custom CSS and JS.

First, in the view editor, on the date custom field, add ‘testimonial-date’ to the CSS classes.

https://www.screencast.com/t/ewwUSTpKO

For example:

.strong-view .testimonial-heading {
  color: purple;
}
.strong-view .testimonial-name {
  color: red;
}
.strong-view .testimonial-date {
  color: green;
}

If that doesn’t work, we may need to increase the specificity in order to override your theme. Likewise if you want to only change one template; e.g. Default but not Modern.

No ‘p’ in heading, name or date.

.strong-view .testimonial-heading {
font-size: 22px;
color: white;
}

.strong-view .testimonial-content p {
font-size: 21px;
color: white;
}

.strong-view .testimonial-name {
font-size: 21px;
color: white;
}

.strong-view .testimonial-date {
font-size: 21px;
color: white;
}