At first glance, the 2019 movie's use of a shade of magenta as the titular colour- which is supposed to have never been seen on Earth before- seems like a bit of a cop-out. However, it's actually a clever decision on the part of the writers: the color magenta doesn't actually exist (our minds produce it in an attempt to form a seemingly-logical bridge between violet and red, even though the two colors actually exist at opposite ends of the spectrum), and what we perceive as magenta is in fact the result of red and blue light being shown to us in equal amounts. The movie, therefore, may be implying that the titular colour is in fact a shade of true magenta, by definition impossible to produce by conventional science and thus never occurring on Earth.
The meteor is still warm the day after it crashed. This is not a case of Lovecraft not knowing his science (meteors cool down immediately), but rather a sign of its unusual nature.
After establishing that the colour's corruption quickly spreads in drinking water, we're reminded that the narrator's initial purpose for coming to the valley was to survey its suitability as a site for a new reservoir to service Arkham.
The fact that most lovecraftian beings are, at best, apathetic or benign towards humanity, there is a very high chance that the Colour itself, is doing everything it does by accident, and example could be in the film, where it fuses the alpacas together, and fuses Theresa and Jack together, it could've not been trying to harm them, but do what energy does, fuse and diffuse, but being an eldritch being, doesn't understand organics can't do that.
