$colors-list : blue, orange, red;

body {
        @each $color in $colors-list{
            @if $color == nth($colors-list,1){
                background-color: $color;
        }
    }
}

header {
    @each $color in $colors-list{
        @if $color == nth($colors-list,2) {
            background-color: $color;
        }
    }
}


.main-width {
        @each $color in $colors-list{
            @if $color == nth($colors-list,3) {
                background-color: $color;
        }
    }
}