CSS change icon color when input is focused

Question

I want the user icon and the lock icon to change color when the input is focused but I don't know how to do could anyone help me please ( I want the icon color to #c0392b )

<div class="input-icons">
     <span class="fa fa-user"></span>
     <input type="text" placeholder="Username">
</div>

<div class="input-icons">
    <span class="fa fa-lock"></span>
    <input type="password" placeholder="Password">
</div>

CSS

@import url(https://fonts.googleapis.com/css?family=Lato:400,700,900);
@import "https://maxcdn.bootstrapcdn.com/font-awesome/4.6.0/css/font-     awesome.min.css";

input {
    padding: 5px;
    border-radius: 20px;
    border: 1px solid #cccccc;
    -webkit-box-shadow: inset 0px 0px 27px -8px rgba(0,0,0,0.75);
    -moz-box-shadow: inset 0px 0px 27px -8px rgba(0,0,0,0.75);
    box-shadow: inset 0px 0px 27px -8px rgba(0,0,0,0.75);
}

input:focus {
    outline: none;
    border: 1px solid #c0392b;
    color: c0392b;
}

input:focus > .fa-user {
    color: #c0392b;
}

.input-icons {
    position: relative;
    margin: 5px 100px 5px 100px;
}

.input-icons > input {
    text-indent: 17px;
    font-family: "Lato", sans-serif;
}

.input-icons > .fa-user {
  position: absolute;
  top: 7px;
  left: 7px;
  font-size: 15px;
color: #777777;
}

.input-icons > .fa-lock {
  position: absolute;
  top: 7px;
  left: 7px;
  font-size: 15px;
  color: #777777;
}

Check out JSFiddle for a preview JSFiddle

Solution

You can use input:focus + .fa css selector do accomplish the task. Notice that I've changed the <span class="fa fa-user"></span> to come after input element.

See more about the plus css selector

More about css selectors

See updated fiddle here

@import url(https://fonts.googleapis.com/css?family=Lato:400,700,900);
@import "https://maxcdn.bootstrapcdn.com/font-awesome/4.6.0/css/font-awesome.min.css";

input {
    padding: 5px;
    border-radius: 20px;
    border: 1px solid #cccccc;
    -webkit-box-shadow: inset 0px 0px 27px -8px rgba(0,0,0,0.75);
    -moz-box-shadow: inset 0px 0px 27px -8px rgba(0,0,0,0.75);
    box-shadow: inset 0px 0px 27px -8px rgba(0,0,0,0.75);
}

input:focus {
    outline: none;
    border: 1px solid #c0392b;
    color: c0392b;
}

input:focus + .fa {
    color: #c0392b;
}

.input-icons {
    position: relative;
    margin: 5px 100px 5px 100px;
}

.input-icons > input {
    text-indent: 17px;
    font-family: "Lato", sans-serif;
}

.input-icons > .fa-user {
  position: absolute;
  top: 7px;
  left: 7px;
  font-size: 15px;
  color: #777777;
}

.input-icons > .fa-lock {
  position: absolute;
  top: 7px;
  left: 7px;
  font-size: 15px;
  color: #777777;
}

<div class="input-icons">
     <input type="text" placeholder="Username">
     <span class="fa fa-user"></span>
</div>

<div class="input-icons">
    <input type="password" placeholder="Password">
    <span class="fa fa-lock"></span>
</div>