Summary
Like many games of this generation,South of Midnightguides players by covering the environment in paint, although its blue version of the idea does at least have an in-universe explanation.
As games get bigger and more ambitious while trying to attract wider audiences, developers have to come up with ways to make sure that most players know what they’re doing most of the time.One of the most prevalent ways this in-game guidance has been done in recent years is with yellow paint, which is often splattered around the world to show the right path.

Despite the nickname,“yellow paint” isn’t always yellow and it sometimes isn’t paint either(shout out to Far Cry’s rope-covered surfaces), but the idea is the same -covering the environment in a substance or surface to make it clear where to go next. South of Midnight is the latest game to do this, but its implementation is at least interesting.
At Least South Of Midnight Tries To Explain Its Yellow Paint
Boo-Hags Beware
When you first start making your way through South of Midnight, you might notice that the climbable ledges and points of interest are all painted blue,which will probably set off your yellow paint alarms. Although it might initially seem like nothing more than a colour change at first, South does actually have an explanation for the paths that Hazel follows.
In the game’s third chapter, you run into a character called Rhubarb and discover something called a bottle tree that’s covered in blue bottles. Hazel takes one of them and uses it as a magical object, but not before talking to Rhubarb, who is wary of her and tells her to stay behind the blue line that’s painted on the floor of his hut.
Rhubarb explains that the blue paint is used to ward off “boo-hags”, which is essentially a catch-all term for mythical creatures and witches. That simple explanation suggests that the world of South of Midnight has been painted blue to keep away the nasty critters and magical monsters found in the South.
The term boo-hag apparently comes from Gullah culture folklore(an ethnic group often found in the Soth), so it’s actually based on a real thing.
Of course, anyone who has played pretty much any game over the past few years will know that it’s really just there to show players the way, but South does at least attempt to make it seem plausible. As an extra point, most of the bottles you’ll see on bottle trees are also blue, which could be for the same reason.