Is it possible to change only the alpha of a rgba background colour on hover?

Question

I have a set of tags with differing rgba background colours but the same alpha. Is it possible to write a single css style that will change only the o

Answer 1

You could do various things to avoid having to hard code the numbers if you want to. Some of these methods only work if you use a plain white background as they're really adding white on top rather than reducing opacity. The first one should work fine for everything provided:

• you aren't already using the psuedo-element for something; and
• you can set position to relative or absolute on the
  tag

Option 1: ::before psuedo-element:

.before_method{
  position:relative;
}
.before_method:before{
  display:block;
  content:" ";
  position:absolute;
  z-index:-1;
  background:rgb(18, 176, 41);
  top:0;
  left:0;
  right:0;
  bottom:0;
  opacity:0.5;
}
.before_method:hover:before{
  opacity:1;
}

Option 2: white gif overlay:

.image_method{
  background-color: rgb(118, 76, 41);
  background-image: url(https://upload.wikimedia.org/wikipedia/commons/f/fc/Translucent_50_percent_white.png)
}
.image_method:hover{
  background-image:none;
}

Option 3: box-shadow method:

A variation of the gif method, but may have performance issues.

.shadow_method{
  background-color: rgb(18, 176, 41);
  box-shadow:inset 0 0 0 99999px rgba(255,255,255,0.2);
}
.shadow_method:hover{
  box-shadow:none;
}

CodePen examples: http://codepen.io/chrisboon27/pen/ACdka