Kat's mother

My assumption would be that Amelia was wearing red when she died, or was dressed in red for the funeral.

According to the director's commentary, the filmmakers wanted to try something different than the usual "angel in white" trope seen in other movies. The director also said that the red was meant to represent Amelia's spunk and her vibrant personality, which was passed down to Kat.

"What's all this gobbledygook here?"
"They're words."

I always assumed it was because the ghosts were white so they wanted her to stand out as different and picked red because it was a good colour choice for the actress and was very vibrant like she was said to have been.

Maybe she had actually gone to hell.

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Consider the daffodil. And while you're doing that I'll be over here looking through your stuff.

good question

"Touchdoooooooooooooooooooooooooooooown Auburn"