(Short) Preamble
My notes, resulting from the “pixel semiotic standard” project, follow. They are grouped by main color-coding, because it (made) makes sense to approach it this way and for the synergistic opportunities to shorten (hopefully) the necessary text, without losing/compromising the contained/intended/inherent information.
Starting with the "Reds":
Reds
Red has a dual (contextual) meaning. Firstly it means: “life, alive, living, sound (adjective)”. Secondly it signifies “alertness, warning, attention”.
[1.] Pressurized Area
This is the sign/symbol that sets the stage/tone (in a way) as it represents the basic living (and livable) space/environment/container (i.e., a/the spacecraft, as defined by the standard).
And. At the same time (and at the symbolic level), the basic shape (and template) for the remaining signs/symbols.
In one sentence. This is the basic container for (many of) the symbol(s) and, also, for the environment that is the object of the semiotic standard: the spacecraft.
The fully closed, unbroken, red enclosing border, establishes a protective bubble that appears filled with white (meaning “life supporting conditions -- pressure and temperature”). It can be equated to the inside of a livable, habitable, operational spacecraft.
It can also be seen to represent safety, a safe place, "the" safe place.
And thus. This design not the first by coincidence.
[2.] Pressurized With Artificial Gravity
Building from the previous (first, #1) sign/symbol, there's a new element here: a red stick figure (representing, undoubtedly, a living, human being, standing in the upright position, considering the circle as the head/face and the rest, by default, the body). Besides directly establishing this as a livable environment, this also establishes the existence of a “floor” and a “ceiling”, and thus, indirectly implies the existence of (artificial) gravity.
[3.] Artificial Gravity Absent
Contrasting/complementing with the previous sign/symbol (in a way, its “antonym”/”antithesis”), there is now an “ungrounded” (i.e., with no point of contact with any surface) figure (representing, again, a living human being) in a, seemingly, upside-down ("unnatural") position. The significance seems clear: no more “floor”-“ceiling”, no more up-or-down.
Without the bounding (artificial) gravity, directions become arbitrary and, thus the "strangeness" (or "awkwardness") of the depiction becomes "undone", orthodoxy returning (normalcy reestablished/restored). In other words, only by removing gravity can the “picture” be fully “accepted” by our (my) brain(s).
Plus.
By his (Ron Cobb's) own admission some of the signs/symbols were indeed semi-humorous and this one surely fits that classification as there is something almost-comical in the upside-down, ”helplessness”, configuration of the depicted figure (which'll be used once more in the standard).
[12.] Hazard/Warning
And now... For something totally different.
This is the sign/symbol with the purpose of informing/conveying that "something" or "somewhere" is dangerous or represents a generic-typed danger.
Because of that nature, it supersedes all of the remaining signs/symbols and their represented information. And because of that. It shouldn't ever be confused with any of the others (signs/symbols). And so. It has to be completely different/distinctive, from all the others. So. The "mold" (template) has to be “broken”. Thus. The shape has to be different from the all others. And has to have red, profusely (remember, the second meaning is: “alertness”).
A small tangent here. This is somewhat similar to the requisites for the STOP sign in use as a traffic/road sign in the world's roads.
And while there is not a universal STOP sign, many of its "manifestations" have an octagonal shape, while being predominantly red (with some white, also).
Drawing inspiration from that (or not), the solution here seems to have started as an all red block, to which four white blocks where added (or cut?) to "break" (differentiate) the original shape.
And. I think. Is no coincidence that the final contour resembles a highly stylized ‘X’ (for "unknown" and/or "do not" and/or "harmful" and/or…, etc.). ‘X’ is used in several symbolic systems to signal "danger", "caution" and "forbidden" so, to my mind, that has probably informed the final design of this sign/symbol.
Oh! And there are also 8 "sides" (counting the alternating white-red outside blocks). In a “special” way, octagonal, too.
[16.] Area Shielded From Radiation
This one is a no brainer. It's a derivation from sign/symbol #2. The bulkier/"reinforced" enclosure (outside red) implies greater shielding/armor/protection from external/exogenous/extraneous conditions/factors (one may assume, because the "human" representing figure is on the inside, where it can benefit from such protection). From that, one can venture that the external "threat" is radiation (which isn't represented, which can either attest to the effectiveness of the shielding or, it’s just a design overlook -- I heavily favor the former).
[20.] Direction / Right-Left / Up-Down
The directional sign/symbol. The arrow points the direction. The only "issue" (I mean detail) that can be mentioned here is the choice of red for the arrow. I think it falls into the "alertness" significance category, so there is (seems to be) an added/heightened level of attention attached to this/these. That seems to be the original intention. Alternatively, if one wanted to detach that "alertness" association from this symbol than the arrow head would have been grey (in lieu of red).
