Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.3.0.rc.1)
// Compass (v0.13.alpha.10)
// ----

@function baseten-hex($number) {
  $hex-values: 0 1 2 3 4 5 6 7 8 9 a b c d e f;
  @if round($number) != $number {
    @warn "base10-hex() needs a integer";
  }
  @if $number > 255 {
    @warn "baseten-hex() numbers need to be less than or equal to 255"
  }
  @if $number < 0 {
    @warn "baseten-hex() numbers need to be more than or equal to 0"
  }
  @return #{nth($hex-values, floor($number / 16) + 1)}#{nth($hex-values,((($number / 16) - floor($number / 16)) * 16) + 1)};
}

@function iehex($color) {
  $hex: opacify($color, 1);
  $opacity: opacity($color);
  
  $alpha: baseten-hex(round($opacity * 255));
  $red: baseten-hex(red($hex));
  $green: baseten-hex(green($hex));
  $blue: baseten-hex(blue($hex));

  @return unquote("##{$alpha}#{$red}#{$green}#{$blue}");
}

$color: rgba(123,123,123,.8);

foo {
  bar: iehex($color);
}

SassMeister-output.css

foo {
  bar: #cc7b7b7b;
}