Generated by SassMeister.com.

SassMeister-input.scss

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

// RGBA IE8 fallback
// based on http://thesassway.com/intermediate/mixins-for-semi-transparent-colors
//
// usage: 
// @include rgba-fallback(rgba(red, 0.6), white);
// @include rgba-fallback(rgba(red, 0.6), white, 'color');

@mixin rgba-fallback($color, $background, $attribute: background-color) {
  $percent: alpha($color) * 100%;
  $opaque: opacify($color, 1);
  $solid-color: mix($opaque, $background, $percent);
  #{$attribute}: $solid-color;
  #{$attribute}: $color;
}

.button {
  @include rgba-fallback(rgba(red, 0.6), white);
}

SassMeister-output.css

.button {
  background-color: #ff6666;
  background-color: rgba(255, 0, 0, 0.6);
}