This thought is not mine, but Ken Hite’s. It’s part of his bloody marvelous Tour de Lovecraft, which should be on everybody’s short list of horror-genre analysis books to buy, but the relevant bit is here:
Hence, you can watch Pleasantville as a photographic negative of “The Colour Out of Space.” As the color which nobody in the world has ever seen before spreads, their society is destroyed. We have met the Colour, and it is us.
No, think about it for a second. Consider Pleasantville as a horror film: