$a: 10;
$b: 5;

@function colorTheme() {
  @return 'red'
}

div {
  @if $a > $b {
    color: red;
  } @else if $a < $b {
    color: yellow;
  } @else {
    color: blue;
  }
}

.test-conditionals {
  @if colorTheme() != 'red' {
    color: red;
  }
  @if colorTheme() == 'blue' {
    color: red;
  } @else {
    color: blue;
  }
}