$colors: (
  blue: #c0392b,
  black: #2980b9,
);
@function style-variation($style) {
  @if map-has-key($colors, $style) {
    @return map-get($colors, $style);
  }
  @error "Invalid color: '#{$style}'.";
}
.container {
  style: style-variation(white);
}