Because it's a stylistic choice. Because it WORKS. Because it feels right and is appropriate to the story and exaggerated feeling of place and time. Because making rhe characters a healthy pink would've been wrong.
Well, the description of Sweeney is "his skin was pale, his eye was odd."
Now, mother always said that whenever you hear a strange, frightening, and potentially life-threatening ghostly chant coming from the dark woods that there's one thing that you should do: Not wake the others and go investigate it alone...