Whites-Greys
White and grey appear as one and the same because, well, they are one and the same. Two colors were needed to create a figure-ground (or figure-background) distinction, allowing the needed details/edges/shapes/patterns to be designed (as it is impossible to paint/draw with just one color -- if it's the same as the background/canvas). With that duality justified, now for the meaning/coding. These colors represent are the normal/neutral/default state. Or. Explicitly: life supporting conditions: pressure, temperature.
[8.] Pressure Suit Locker
In the usual protective shell (the red, continuous, border) the same pressure suit (from signs/symbols #13 and #14) appears, but, this time, in an "unnatural" position (as if it is not being worn/used). This is reinforced by the lack of a red "face" (in lieu of a better designation...) where one could/should/would be (as seen in #13/#14). All of the above seems to indicate some kind of storage place for unused pressure suits. Which seems to exactly match the original design intention.
[9.] Photonic System (Fiber Optics)
A pretty straight-forward one. There is an undulating, weaving, pattern traversing the interior space, which, in hindsight, seems a simple but apt representation of a fiber optics network. The really clever design bit is (are) the broken spaces, cut in the protective spacecraft enclosure (the red layer). It seems, to me, to convey two different, and yet, concurrent ideas: 1, the fiber optics network is not confined to the interior of the spacecraft but also connects to exterior areas of the same spacecraft (which makes perfect sense, e.g. to access external sensors) and, 2, the notion of input-output with the outside, allowing from cabled communications with the exterior (which also seems not only proper, but, also, necessary).
[10.] Laser
This one is very (very) clever. There is a diamond/rhombus shape in the exact center/middle. From each vertex there is a "beam" emanating outwards that is not stopped/blocked (stoppable/blockable) by the spacecraft enclosure (in red). Another way to see it: there are 4 triangles (triangles are used in several places throughout the standard as some kind of force/effect carrier/originator, so the 4 overlapped triangles seem more probable as the original intention). The four-directions seem to hint at the multidirectional nature of the laser(beam) and the 4 holes in the protective/surrounding layer seems a dire warning to the terrible consequences of mishandling this specific piece of hardware.
All in all, it seems to be "saying": Beware! Be careful where you point this as it can be pointed anywhere and it can make terrible damage to this spacecraft".
However.
It could have been red (matching the "alertness" significance), where is grey, but, I think, the relative small size (and power) of the laser would not warrant a greater alertness level. If the (interior) laser were to be bigger and more powerful, then red (instead of grey) would, definitely, be the way to go.
[11.] Astronic System (Electronics)
This can be compared to sign/symbol #9 (Fiber Optics). This one, instead, depicts Electronics. It does so by using the complementary polarity signs (+/-) in a complementary way (the colors are reversed between them, both the sign and its background). What "connects" (I use this term loosely here) with sign/symbol #9 are also the "gaps" in the (red) enclosure. Here, I believe with the same, dual, meanings: possibility of input-output with the exterior and also the existence of electronic elements on the outside of the spacecraft.
[21.] Life Support System
This one is a bit generic (as I see it, OC). I mean. A central(ized) rectangle appears, from where multiple "channels" connect, in a distributed fashion. And. So. It seems to have a central(ized) part and it also seems to be a pervasive system... Doesn't exactly "lock" "Life Support System" as a definite and unambiguous meaning. However, if one revisits the original color-coding significance of white-grey: "life supporting conditions: pressure, temperature" for that, the (intended) result doesn't become such a stretch.
24. Bridge
A white, isosceles triangle, framed/defined/enveloped by a grey background, appearing to point upwards (and, I venture, outwards). I think there is a dual meaning here too (which has to do with location/placement, for "upwards", and also, with function, for "outwards"). Firstly, location/placement. Researching the origin of the word "Bridge": "With the arrival of paddle steamers, engineers required a platform from which they could inspect the paddle wheels and where the captain's view would not be obstructed by the paddle houses. A raised walkway, literally a bridge, connecting the paddle houses was therefore provided". A raised platform. That takes care of the "upwards" part. For the "outwards" bit. Also from the same Wikipedia entry (for "Bridge"): is the room or platform from which the ship can be commanded". If one adds to this notion what was already referred for "triangles": as a representation of a force/effect carrier/originator. Then. "A place of command, that can originate a force/effect that can impact what goes on outside". Seems a good representation of the functional aspect of a Bridge. Clever!
26. Maintenance
Two, connected, chain links. Do not exactly "scream" "maintenance" to me. However. Investigating further. There are chains in the movie (according to a trivia item – check the jumps below for a direct link to it -- in the IMDb's "Aliens" entry, chains were a point of contention between Ridley Scott -- who wanted them -- and the producers -- who didn't want them) and , maybe, just maybe, that "discussion" may have informed the "need" for such design. Having a sign/symbol depicting chains and then no chains in the movie would have been "strange" (at least). OC, this is pure speculation. Grain of salt and all that.
27. Ladderway
A ladder. Ladderway. The only thing to remark in this one is how the ladder(ways) appearing in the movie are actually fashioned after this same design (or is it the other way around? The chicken or the egg?)
28. Intercom
This one is a bit of a puzzle. So I'll use what was learned in all the other (previous) designs. Using the convention (already used) of top-down, left right, I'll start at the top-left. A grey block, ending in a triangular shape "points" right. According to the previously acquired knowledge there is something originating/going from left to right. Advancing towards down-right there is a similar block, only reversed (symmetrical), going/originating from down-right. The misalignment seems purposeful and, thus, seems to indicate that they do occur concurrently, more like alternating in time. A two-way alternating process. It's a (rather) vague depiction of inter-communication(s), but, still, an acceptable one, I think.
29. Storage / Non-Organic
The protective (red) enclosure contains another enclosure which contains something. That seems an apt/sufficient enough depiction of "Storage", to me.
30. Computer Terminal.
It. Is. A. Computer. Terminal.
