I dont have any experience playing shadowrun but i have been a fan for a really long time. I've played the games(snes/sega), own tons of the novels and baught some of the rulebooks and over the years i have had my very own understanding of the world of shadowrun lol.

One of the things i thought was contradicted in a thread on here, so i went and tried to find something in the rulebook to back up my opinion but i couldnt find anything. Maybe i read it once before but i couldnt find it now so......

In astral space they said that things like rocks and walls are kinda greyed out and are like shadows of thier physical side. I kinda always thought that made them kinda see trhough.

So is a physical wall in astral see through at all?? I always thought you could see through it, you just couldnt cast through it. Im probably just assuming the wrong thing but maybe i read it someplace somewhere lol. So whats the answer?

Not sure where it is printed, but generally, If you can't see through it in the physical woulrd you can't see through it in the Astral.

From what I understand, Non-living items have a dull grey shadow on the Astral. This does include walls ect.
The question does come with items that are normally transparent in some +frequencey's but not in others. Today's glass for example.

Think of the greyed out look like this: anything not alive or with a stron astral impression tends to look like it was passed though a vibrancy reducing filter. Basically, things like the painted color of the walls, the color of the floor tiles, and so on will be much 'dimmer' that it is vs normal vision. In general it's things living things and things that people really care about (or are really afraid of) that look full color on the astral.

Indeed. In fact, most living things have added "color" to them that might vaguely resemble an infrared scan, a strange overlayed "vein map", a full body halo glow (a classic version of an aura), or a strange out of sync double image. These additional images likely vary depending on the character perceiving at the time (tradition, player pref, GM pref, and so on) and are representative of a persons aura.

Said auras don't seem to make a person more visible on the astral, any kind of stealth skill (besides disguise) can fool a perceiver almost as easily as on the physical plane. However, spell effects seem to. In addition to the lighting and visibility mods from the physical plane, you have additional variables from spells and various magical effects. Perhaps certain spells not only make the target more visible, but might offer up lighting to reveal other living auras. This last part is the GMs discretion.

At times, according to previous SR canon, there might be actual places that exist on the Astral that do not on the Physical. These are called Astral Constructs and can seem surreal or even like the Physical plane itself, depending. Powerful spirits often dwell within these phenomena.

More for flavor than anything else, I ruled a while ago that glass was opaque on the Astral plane. That might have to go away, though

Part of Infiltration isn't just being unseen it is acting in such a way that makes those who see you believe that you belong there, while avoiding any serious alarm triggers.

So what if the Corp Mage see me Astrally. Just so long as he believes that I am just another Company employee, or doesn't care because it is late and he want to get home to his wife and kids, and doesn't view me as a possible threat.

Also, bear in mind that the cosmology canon does change from edition to edition. Example: SR3 indicates that:

"Speech and other sounds are as easy to hear from the astral plane as they are in the physical world."

...where SR4 changes this to be:

"Things that exist only on the physical plane can be seen and heard from the astral, albeit with blurred features and indistinct sound -- emotional content registers far more strongly than exact details."

So from just SR3 to SR4 suddenly you can't really hear stuff on the Physical plane from the Astral without Manifesting. And let's not forget the loss of grounding spells through foci.

The purpose of this post is to point out that canon changes from edition to edition and it's not always helpful to look at past editions for guidance. The writers of SR4 have apparently assumed that everyone is a new player.

That being said, treat it as you like in your game. SR4 offers no clear guidance on whether walls can be seen through or not. The use of the word "faded" can be interpretted many ways. In my game, physical objects are translucent, similar to Astral Barriers, and like Astral Barriers they merely impose a Perception Test penalty equal to the barrier's Force. I treat this like a thick sheet of tinted clear plastic. Seeing through multiple objects is simply a matter of adding the barrier ratings together for a Perception Test penalty. In this manner, buildings very, VERY quickly become impossible to see though completely, and while walls are translucent, they are not transparent... an action must be spent on the Perception Test to attempt to see through one. A crate in a warehouse is the same... imagine a translucent box with translucent objects inside: a perception test could easily tell you there are weapons inside. It's not canon, but it's the way I like it.

Note: See info on the subtle difference between transparent and translucent here.