Change one property in CSS

I have this CSS style:

.bx--text-area:disabled {
    position: relative;
    border: none;
    padding: 0;
    -webkit-box-shadow: none;
    box-shadow: none;
    pointer-events: none;
    background: #e5e5e5;
    color: black;
    height: 6.25rem;
}

And I want to change just the color property without copy-pasting the whole style in to my css stylesheet.

How can I do that? Is that possible?

.body{
  color:black;
     }

.commanClass
{
  height:100vh;
  width:100%;
}

.bg1
{
  background: red;
}
.bg2
{
  background: blue;
}

<div class="commanClass bg1">  
</div>

<div class="commanClass bg2">  
</div>