normal_image = new Image();
normal_image.src = "img/homeButtonWhite.png";

mouseover_image = new Image();
mouseover_image.src = "img/homeButtonGrey.png";

normal_image1 = new Image();
normal_image1.src = "img/AboutMeWhite.png";

mouseover_image1 = new Image();
mouseover_image1.src = "img/AboutMeGrey.png";

normal_image2 = new Image();
normal_image2.src = "img/projectsWhite.png";

mouseover_image2 = new Image();
mouseover_image2.src = "img/ProjectsGrey.png";

normal_image3 = new Image();
normal_image3.src = "img/ContactMeWhite.png";

mouseover_image3 = new Image();
mouseover_image3.src = "img/ContactMeGrey.png";



<!-- repeat the 4 lines above for any subsequent images. -->

function swap(){
if (document.images){
for (var x=0;
x<swap.arguments.length;
x+=2) {
document[swap.arguments[x]].src = eval(swap.arguments[x+1] + ".src");
}
}
}