Generated by SassMeister.com.

SassMeister-input-HTML.html

<div id="parentA">
  <span>hello!</span>
</div>

<div id="parentB">
  <span>hello!</span>
</div>

SassMeister-input.scss

// ----
// Sass (v3.4.21)
// Compass (v1.0.3)
// ----

@mixin textColor{
  span{
   color: green;
  }
}

#parentA{
  width: 100px;
  height: 100px;
  background-color:blue;
  color: black;
  @include textColor;
}


#parentB{
  width: 100px;
  height: 100px;
  background-color:red;
  color: black;
  @include textColor;
}

SassMeister-output.css

#parentA {
  width: 100px;
  height: 100px;
  background-color: blue;
  color: black;
}
#parentA span {
  color: green;
}

#parentB {
  width: 100px;
  height: 100px;
  background-color: red;
  color: black;
}
#parentB span {
  color: green;
}

SassMeister-rendered.html

<div id="parentA">
  <span>hello!</span>
</div>

<div id="parentB">
  <span>hello!</span>
</div>