// set your color
$backgroundColor: red
// set the scale/increment for the function
$backgroundColorScale: 8
// number of items in your list
$numberOfItemsInList: 10
// here's a custom function to change the color
// but you could make this fairly advanced
// and shift color, saturate, etc.
@function -modify-bg($bgcolor, $counter, $depth: $backgroundColorScale)
@return lighten($backgroundColor, ($i * $backgroundColorScale))
// here's the loop that steps through LIs and assigns each a new bg
$i: 0
@while $i < $numberOfItemsInList
li:nth-child(#{$i})
background-color: -modify-bg($backgroundColor, $i)
$i: $i + 1