Comparing Bitmap Pixel Data To BufferedImage?

I'm working on a project based on Roger Alsing's Mona Lisa evolution.

My problem seems to be that when I compare the RGB values of the target image and the randomly generated image, I don't get a representative result of how "close" the two images are.

I load the target image (a 24-bit bitmap) using:

img = ImageIO.read(new File(filePath));

I draw onto a BufferedImage with:

for(int i = 0; i < numPolys*12; i += 12){
p[(int)(i/12)].addPoint(gene[i], gene[i+1]);
p[(int)(i/12)].addPoint(gene[i+2], gene[i+3]);
p[(int)(i/12)].addPoint(gene[i+4], gene[i+5]);
p[(int)(i/12)].addPoint(gene[i+6], gene[i+7]);
Color mycol = new Color(gene[i+8], gene[i+9], gene[i+10], gene[i+11]);
gf.setColor(mycol);
gf.fillPolygon(p[(int)(i/12)]);
}

And I compare the BufferedImage with the target image using:

for(int x = 0; x < inGene.x; ++x){
for(int y = 0; y < inGene.y; ++y){
Color mycol1 = new Color(exp.getRGB(x, y));
Color mycol2 = new Color(inImage.getRGB(x, y));
int delta = mycol1.getRed() - mycol2.getRed();
score += (delta * delta);
delta = mycol1.getGreen() - mycol2.getGreen();
score += (delta * delta);
delta = mycol1.getBlue() - mycol2.getBlue();
score += (delta * delta);
}
}

My problem is that my code runs to a certain point, where it seems no matter what happens to the image, it doesn't seem to get any closer to the target image.