The photons "in space" are in space - they haven't yet reached your eyes. We ONLY see light when it actually reaches our eyes. Think of a stream of photons - one behind the other. We see them when they hit our retinas - the ones still in space (that you think should make the space look red) are still in space on the way to our eyes. We do not (and cannot) see the entire stream on its way to our eyes.
We measure the distance between objects. (We don't see the space). We see objects in space. We don't see space around and between objects we see the absence of objects. If we could actually see space then we'd effectively be blind (like having a permanent wall directly in front of our us whichever way we turned - all we would see would be the space directly in front of us).
It sounds rather strange to me that we do not see space. I am sitting here now looking at the space between myself and the wall. I am considering your wall, does the object you are viewing allow you to see through this wall?
We "see" the photons that strike the retinas of our eyes. These form two dimensional images, which are transmitted to the visual center of your brain which takes those images and a number of clues (eye convergence, the stereoscopic effect caused by having two eyes, convergence due to perspective, etc.) to "recreate" a model of the 3D world around us in our head. We do not "see" the space around and between objects as much as extrapolate it from what we do see. Of course this extrapolation is not always perfect, which is why optical illusions such as this one are possible. Please Register or Log in to view the hidden image! The shape of the room, and size of objects on the walls create visual clues that fool your mind into thinking the that two men are an equal distance away, and that one man is much larger than the other. In truth, the smaller seeming man is much further away, and you have been fooled by false perspective. Your mind extrapolated the shape and size of the room, along with the apparent locations of the two men incorrectly. If you directly saw or sensed 3D space, this illusion would not work.
So in the expansion of space which uses light in the red-shift, how are we seeing an expansion of space?
No you're not - you're looking at the absence of objects. Given that I stated that we'd be effectively blind what do you think? If we could actually see space then it would block everything else behind it (given that there's always space between our eyes and whatever we look at) - we can't see objects behind other other objects so we wouldn't see objects behind the space in front of our eyes.
Well, that's what we in the physics trade call a figure of speech. What you meant to say was, you're looking at the wall and measuring (approximately) a distance from you to it. If there's nothing you can see between you and this wall, you call it "space". Space-- lit. "the absence of visible objects" (from the dictionary of physics inside my head, put there by several years of university). Ahem.
Wiki is your friend: The metric expansion of space is the increase of the distance between two distant parts of the universe (i.e. gap between objects) with time. We don't see "space expanding" we see the distance between things getting bigger.
Well, yeah. It does if there's more than one object. If, say, you count yourself as an object like you do when "you" look at a wall. Suppose you have two numbers. What's the distance between them if they aren't the same number? What's between 1 and 2 if they aren't real numbers?
https://en.wikipedia.org/wiki/Big_Bang The big bang suggests the Universe is expanding, from what you have explained about sight , is it not just the distance of observation that is expanding?