Assign random colors from an array

gistfile1.sass

$colors: $color-vivid-red,$color-vivid-red-medium,$color-vivid-red-dark,
$color-dark-blue,$color-dark-blue-medium,$color-dark-blue-dark,
$color-moderate-blue,$color-moderate-blue-medium,$color-moderate-blue-light,
$color-vivid-orange,$color-vivid-orange-medium,$color-vivid-orange-light;

$colors-length: length($colors);
background-color: nth($colors, random($colors-length));

@for $i from 1 through 4 {
    &:nth-child(n + #{$i}) {
        background-color:nth($colors, random($colors-length));
    }
}