CSS position child under it's parent - html

Question

Is it possible to position child element (C) under its parent (B), and above B's neighbor (C)?
It's a little bit difficult to describe, you can watch example here.
The question is to position blue div.inner above red div.neighbor AND under green div.outer.
To illustrate:
HTML code:
<div class="neighbor"> </div>
<div class="outer">
<div class="inner"></div>
</div>
CSS code:
.neighbor{
background-color: red;
height: 500px;
width: 500px;
}
.outer{
background-color: green;
width: 300px;
height: 300px;
position: fixed;
top: 0px;
left: 0px;
}
.inner{
background-color: blue;
width: 100px;
height: 100px;
position: fixed;
top: 0px;
left:250px;
}

Answer 1

JsFiddle
HTML:
<div class="red"></div>
<div class="green"></div>
<div class="blue"></div>
CSS:
.red {
background-color: red;
height: 500px;
width: 500px;
z-index: 1;
}
.green {
background-color: green;
width: 300px;
height: 300px;
position: fixed;
top: 0px;
left: 0px;
z-index: 3;
}
.blue {
background-color: blue;
width: 100px;
height: 100px;
position: fixed;
top: 0px;
left: 250px;
z-index: 2;
}

Answer 2

.neighboor {
background-color: red;
height: 500px;
width: 500px;
position:fixed;
z-index:-200;
}
.outer {
background-color: green;
width: 300px;
height: 300px;
position: absolute;
top: 0px;
left: 0px;
}
.inner {
background-color: blue;
width: 100px;
height: 100px;
position:relative;
z-index: -100;
top: 0px;
left: 250px;
}