HTML - Javascript | Keep Colors Page to Page?

[Baseball Freak]

So in my site, my I use index.php because I include head.htm and foot.htm and put my text into the index.php. In head.htm, I have this code that changes my background color:

<form action="#" onsubmit="return change_it();">
<select name="change_bg" id="change_bg">
<option selected="selected" value="0">Select Background</option>
<option value="1">Default</option>
<option value="2">Black</option>
<option value="3">Red</option>
<option value="4">Green</option>
<option value="5">Blue</option>
<option value="6">Yellow</option>
<option value="7">Turquoise</option>
<option value="8">Pink</option>
<option value="9">Gray</option>
<option value="10">White</option>
</select>
<input type="submit" value="Go!" />
</form>
<script type="text/javascript" >function change_it() {

if (document.getElementById && document.createTextNode) {

var new_color = "";
var color_sel = document.getElementById("change_bg").value;
color_sel *= 1;

switch (color_sel) {
case 0 : window.alert("You will need to select a color before you can change it."); return false;
case 1 : new_color = "#303030"; break;
case 2 : new_color = "#000000"; break;
case 3 : new_color = "#FF0000"; break;
case 4 : new_color = "#00FF00"; break;
case 5 : new_color = "#0000FF"; break;
case 6 : new_color = "#FFFF00"; break;
case 7 : new_color = "#00FFFF"; break;
case 8 : new_color = "#FF00FF"; break;
case 9 : new_color = "#C0C0C0"; break;
case 10 : new_color = "#FFFFFF"; break;
}

document.body.style.backgroundColor= new_color;
return false;

}

}</script>

How can I make it so that the background color will change if I click on another link in my website with the same style and stuff.