Glo screen reversal

I bought my Glo about month ago and, in general, am happy with it. When reading a book, and I touch the right edge to turn the page, the screen momentarily goes from black text on light background to white text on black background, then back to black text on light background for the new page. This all happens quickly and is not a real problem, but I do wonder if this is normal and whether there is some setting that will stop this from happening. Thanks,
Ted