I love that description! It's very funny.
To answer your question: VioletNightro first came up with the idea of a "lame" horror painting game in which you paint a black piece of paper, one that represented "darkness", and then I added the monster twist shortly after. Originally, you would simply paint the picture to reveal a "scary" monster, but the idea soon evolved into what Paint in the Dark ended up being: paint the picture and avoid painting any monsters to not get jumpscared. The game was envisioned to be part memory game and somewhat trial and error without being unfair.
The "horror" aspect was initially meant to be satirical and very lame (because it's Lame Jam), but we ended up loving the concept so much that the lame aspect flew over our heads, even though "make a lame game" wasn't a strict rule for this jam. We're very happy with how the game turned out in the end.