How to reference variables in a map, before the wh

I’ll start with my code, as it should be easier to understand what I want to do:

@function get-color($color, $lightness) {
  @return map-get(map-get($colors, $color), $lightness);
}

$colors: (
  green: (
    light: #A4EDE1,
    mid: darken(get-color(green, light), 20%),
    dark: darken(get-color(green, mid), 20%)
  ),

  red: (
    light: complement(get-color(green, light)),
    mid: complement(get-color(green, mid)),
    dark: complement(get-color(green, dark))
  )
);

As you can see, I have created a multidimensional map, with my color values.
At the moment, I want to create the other colors, through the darken() and the complement() functions. The problem with that is, that I need to reference variables inside of the $colors variable, before it is completely filled. This results in an error for my get-color() function, which tells me, there is no $colors variable.

I know it would be possible to alter the colors outside of my $colors map, but the benefit of doing it this way is, that I can always come back and define color values, that are not generated. This would be a huge benefit in maintaining the project.

So here my question: Is there any way to reference another variable in map, before the whole map is defined?

No. The mapping isn't defined until you reach that semicolon at the end. So you cannot reference any portion of it until then.

$base-color: #A4EDE1;
$colors: (
  green: (
    light: $base-color,
    mid: darken($base-color, 20%),
    dark: darken($base-color, 40%)
  ),
);

$colors: map-merge($colors, (
  red: (
    light: complement(get-color(green, light)),
    mid: complement(get-color(green, mid)),
    dark: complement(get-color(green, dark))
  )));

.foo {
  color: get-color(red, mid);
}

Unless you're looping over the mapping, I would recommend not using mappings to store your color variables. Rather, it would be better to simply write a function that will do the manipulation for you:

$base-color: #A4EDE1;

@function get-color($lightness, $variation: null, $color: $base-color) {
  $color: if($variation, call($variation, $color), $color);

  @if $lightness == medium {
    @return darken($color, 20%);
  } @else if $lightness == dark {
    @return darken($color, 40%);
  }
  @return $color;
}

.foo {
  color: get-color(mid);
  border: 1px solid get-color(mid, complement);
}