The painting colors are highlighted, nothing else as far as I remember. Easy enough to figure out it has something to do with the paintings, but it also requires you to realize each painting represents a cardinal sin, plus remember each book of sins has a numbered volume and that makes up the code... a bit of a stretch for a porn game... Ofc course in hindsight it makes total sense, but not that straightforward if you have no clue what to expect.
If viewing the paintings prompted a line like. "she looks GLUTTUNOUS" or something like that, would be helpful
I know, but what I'm saying is, players shouldn't have to resort to guides outside the game to figure out mandatory events. Just my 2 cents