:root {
  --lighter:  #ccc;
  --lightest: #fff;
  --darker:   #999;
  --darkest:  #444;
  --background: pink;
}

header, footer { background: var(--darker) }

aside {
  --background: pink;
  background: pink;
}

aside {
  background: var(--background);
  display: block;
  background: pink;
}

:root {
  --lighter:  #ccc;
  --lightest: #fff;
  --darker:   #999;
  --darkest:  #444;
  --background: pink;
}

header, footer { background: var(--darker) }

aside { background: var(--background) }

Change background color for IE browsers
Change background color for IE browsers
