(Extremely minor Watcher's Keep spoilers)
Lum the Mad is the guy who built the machine at level four and left notes allover the keep hinting at how to get goodies out of it. Lately I've been thinking, some of the combinations are actually intuitive, poetic, or at least not entirely arbitrary.
Strength: Square, short, medium
Dexterity: Square, blue, short
Constitution: Circle, red, long
Intelligence: Circle, blue, long
Wisdom: Circle, square, triangle
Charisma: Red, green, short
Magic resistance: Blue, green, long
Storm Star (Mace +3): Triangle, green, medium
Portal to next level: Triangle, red, medium
A few of these, I find to be quite fitting.
Constitution: Will keep your blood (red) pumping (circulating) a longer time.
Intelligence: Replace blood with mana. D&D doesn't use mana, but higher intelligence can be thought of as more mana in the sense of more memorization slots. I can also name other games where int=mana.
Charisma: You go from red light (no) to green light (yes) in a short time because you are so damn persuasive!
Magic resistance: Magic users, as represented by the blue mana, will be jealous (green) of you for a long time.
Three others, I have weaker explanations for.
Storm Star: Triangle could represent the flanges, medium could just be the weapon size. It's not a two-hander but it's also not a dagger. Got nothing to explain the green part.
Portal: A red triangle is a warning in traffic, and there are certainly dangers below. Of course, D&D doesn't use traffic signs and I can't explain the medium part.
Wisdom: I bet you could get philosophical about this one whatever the combination was, but heyyyyyy, yooo, you realize a circle, square and triangle can all be drawn with one continuous line? Crazy shit, right?