IMO, it immediately strikes as a metaphor for generational garbage collector, each region depicting the generation of objects: red => new, blue => long-lived, b

IMO, it immediately strikes as a metaphor for generational garbage collector, each region depicting the generation of objects: red => new, blue => long-lived, black => garbage collected, whiteness => (??) the programmer doesn't have to worry about those details. While the rectangular shapes denote perfect building blocks, it would have been better to mix them with curves, as an expression of finesse, and/or surgical precision. Later, pg's comment at arclanguage.org says that it's "a." May be the lack of curves is intentional, to caution that abstractions are often somewhat approximate? :)