Ioslides for Rmarkdown have this gradient background, and I would like it to be solid white.

I tried two different ways to remove the gradient effect using a css file, but neither have been successful.

body {
  background-color: white;
}

slide {
    background-color: white;
}

An online demo of the problem is here:

You were trying to set the background-color, but it's actually a background-image that has the gradient.

If you add the following css rule

slides slide { background-image: none; }

The gradient is removed: