Different kinds of characters will concentrate on different things. There's the painfully shy girl who probably couldn't tell you what anyone wore, ever, and could never identify a killer if their life depended on it, even if they were in the room and ostensibly witnessed the killing. She might be able to tell you if the floor had been swept though, or what color socks she wore yesterday, probably every day of the week. This kind of character might not even notice what color the walls were painted or whether the curtains were open or closed.
There is the guy who might notice a coat only if it could conceal a gun, like Bourne in Bourne Identity. He might be able to tell you such things as how many men are in the room and if any of them might be inclined toward fighting, if they were ever challenged and not given the chance to run away.
Police officers are trained to notice a lot in a short period of time. They notice people, colors, and environment. Don't get me wrong; I'm no cop, but don't make your cops supernatural in their visual acuity.
With these variations in mind, you now need to consider your character's setting. The instance I have in mind came from the book I'm reading at the moment. This guy, a police detective, was strapped to a bed. He had been drugged, and though I suppose it's possible, waking to instant alertness seems a little off to me. I'm not questioning that though. The first thing he did was look around. That's fine, but if you're strapped to a full sized bed (specified in the book) I'm thinking you're not going to notice anything about the floor. Also, since he was tarazed and then drugged prior to being brought here, taking note of the decor might not be at the top of his to-do list, but he's a cop and he was looking around. He noticed wall color, ceiling color, the fact that the overhead light was hooked up oddly. Now, the floor was also described, but really, strapped flat on your back, the floor can't be seen and a cop might not bother with the floor, even if he was standing on it. His concern with the floor would revolve around traction. You might be surprised at how few people really take note of floors.
Another thing he noticed, that the writer was trying to clue us into early (maybe too early), was that at least one wall was curved. Now unless that wall was VERY curved, meaning the dome was rather small, such an anomaly wouldn't have been noticed in that first look-around. There were other details that were there for the writer's benefit, that probably wouldn't have attracted a second thought, not right off the bat. I mean, he has other things far more pressing to worry about right in that moment. There were strange people in the room. He didn't know where he was. Not to mention the fact that they had him strapped down. Not exactly the circumstances where one mulls over the decor.
In this description of a curved wall, one wrong word turned the whole thing topsy-tervy. The wall was said to be the 'back' wall. Now, go back to the orientation of your character, flat on a bed. Where would this 'back' wall be? Where is the door? Where is the bed in relation to the door? Did he need to look down past his left foot to see the door? Was the 'back' wall, the wall behind his head? No, there wasn't any window, but he made no mention of that little detail. How many rooms have you been in that didn't have a window? Would you notice the lack if you found yourself waking up in such a room? Would you think 'basement' first and maybe test the air to see if it smelled like one?
So, just remember when describing your scene. Remember what you can see, and remember what isn't there as well. Remember what is within his range of view and filter it by importance to the moment. In the case of this book, there was plenty of time to reinforce the roundness of the location and why there was no windows. Just beyond the door was culvert-shaped halls leading to and from divided and undivided domes the place was made of. He got a tour pretty much first off, so telling us in the first scene that one wall was not flat was a bit of overkill in the wrong place.You have the whole book to cover all the bits and pieces of scene surrounding your character; you don't need to crowd it all in all at once.