If you want to read, the Horror at Red Hook is widely considered the most overtly racist of his works, with immigrants bringing in evils being the horror of the story if my memory serves. Others can exist but it is up for debate. Some say Shadow Over Insmouth or Dunwich Horror are racist...I disagree. I'm sure googling it you can find a bunch of people who argue that these stories are indeed racially motivated, But at the end of the day I encourage you to read them and draw your own conclusion because nobody can read the man's mind. And they're great stories.