Transition background-color via slide up animation

Question

I am trying to change the background-color of an element on hover by using CSS transitions. I want to do this by having it scroll up from the bottom. I can fade the backgrou

Answer 1

An extension to @Sampson answer where I will consider more friendly values easier to understand:

.box {
  width: 100px;
  height: 100px;
  display:inline-block;
  background-size: 200% 200%;
  transition: background-position 1s;
}

.to-top{
  background-image: linear-gradient(to top, red 50%, black 0);
  background-position: top;
}

.to-top:hover {
  background-position: bottom;
}

.to-bottom{
  background-image: linear-gradient(to bottom, red 50%, black 0);
  background-position: bottom;
}

.to-bottom:hover {
  background-position: top;
}

.to-left{
  background-image: linear-gradient(to left, red 50%, black 0);
  background-position: left;
}

.to-left:hover {
  background-position: right;
}

.to-right{
  background-image: linear-gradient(to right, red 50%, black 0);
  background-position: right;
}

.to-right:hover {
  background-position: left;
}

<div class="box to-top"></div>

<div class="box to-bottom"></div>

<div class="box to-left"></div>

<div class="box to-right"></div>

Here is more fancy transitions:

.box {
  width: 100px;
  height: 100px;
  display:inline-block;
  transition:  1s;
}

.to-center{
  background: 
    linear-gradient(black,black) no-repeat,
    red;
  background-size: 100% 100%;
  background-position:center;
}

.to-center:hover {
  background-size: 0% 100%; /* Or 100% 0% */
}

.from-center{
  background: 
    linear-gradient(red,red) no-repeat,
    black;
  background-size: 0% 100%;  /* Or 100% 0% */
  background-position:center;
}

.from-center:hover {
  background-size: 100% 100%;
}

.diagonal-right{
  background-image:linear-gradient(to bottom right,red 49.5%,black 50%);
  background-size: 200% 200%;
  background-position:bottom right;
}

.diagonal-right:hover {
  background-position:top left;
}

.diagonal-left{
  background-image:linear-gradient(to bottom left,red 49.5%,black 50%);
  background-size: 200% 200%;
  background-position:bottom left;
}

.diagonal-left:hover {
  background-position:top right;
}

<div class="box to-center"></div>

<div class="box from-center"></div>

<div class="box diagonal-right"></div>


<div class="box diagonal-left"></div>

Related question to get more details about how background-position works combined with background-size: Using percentage values with background-position on a linear gradient

Answer 2

In order to slide the background color up you would need to use a background image, or a gradient of some sort, while gradually adjusting the background-position:

.box {
    width: 200px; height: 100px;
    background-size: 100% 200%;
    background-image: linear-gradient(to bottom, red 50%, black 50%);
    transition: background-position 1s;
}

.box:hover {
    background-position: 0 -100%;
}

You can see this demo here: http://jsfiddle.net/as5ZU/