use Win32::GUI;

$screen = new Win32::GUI::DC("DISPLAY");

while(1) {
    ($x,$y) = Win32::GUI::GetCursorPos();
    $color = $screen->GetPixel($x,$y);
    next if $color eq $last;

    $last = $color;
    printf ("%06X\n", $color);
    sleep 1;
}