Why do I see two different colors when using {background-color}?

[ghost]

Description

Hello there,

When customizing a slide background with

## Slide backgrounds {background-color="#806040"}

Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua.

it renders a slightly different colored rectangle around the content part. See screenshot:

There is nothing fancy in my presentation, that to my knowledge could cause this odd behaviour. The YAML header is quite basic:

---
title: "My title"
format:
 revealjs:
   incremental: false
   scrollable: true
   theme: dark
editor: visual
mainfont: avenir
---

Can anyone help me out with this?
Many thanks in advance!

[cderv]

DO you have any other customization ? I can't reproduce with this

---
title: test
format:
 revealjs:
   theme: dark
---

## Slide backgrounds {background-color="#806040"}

Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua.

[ghost]

Thanks for your reply. No, I do not have any further customization. However, I finally quit RStudio and re-rendered the presentation. Then it was gone. Still odd, why it occured in the first place.