If it gave out, perhaps the mood might be lightened.
I think it's unclear as to what 'it' is in this sentence. The figure? The chair? The mood?
If no one else has started writing a continuation yet, I will, and edit this post with the results. Elsewise stop me now.
edit: okay
The figure - revealing itself in the light to be just that; a figure, androgynous, humanesque but undefined, a gesture of the person that it had probably once been - glanced back into the tight space. Its eyes lazily drifted to each hole in the black of the window, reassuring itself of the persistence of the light that trickled through. Not a trick of its broken mind. Not a wishful thought made briefly visible through wishing hard enough. The flashes of light indeed persisted, and with a certain regularity, even.
The figure turned once more to face the bright and verdant green (that was still somehow dead for all its vivacity) and took a few tentative steps out into it, turning briefly only to close the door, tenderly, behind. With the 'ch-click' of the closing door, the fluorescent green light dimmed to a more human piss-gray.
The new light recalled Old Man's natural habitat: factories and offices and stale, routine, indoorsy places. The place reflected it, too - or a twisted parody of such locales: a narrow hallway floored with broken and filthy porcelain tiles, many missing. Walls lined with wallpaper of indeterminate pattern, peeling and soggy for some reason (as if there were some invisible ghost who made a job of going around and sogging everything). An electric hum sounded from behind a frosted glass ceiling - strangely whole, strangely clean - that emanated that fluorescent green and, now, the piss-gray light. At either end of the hallway was an old wooden door just large enough to reach from one wall to the other, and from the ceiling to the floor. Or maybe the hall was just large enough to accommodate the doors.
The figure, standing in the middle of the hallway looking something like a wisp of person, began to move towards the door on its left. Feet bare and black from filth, it went in a strange, slow, rhythmic sort of dance. The figure stepped deliberately, carefully scouting out the next sane footfall before slowly lifting its leg, wiping the spot off with its heel in a sweeping motion, and then firmly planting its foot down, squelching as it went, a victim of the sog-bringer. The figure continued this odd motion down the hallway: pause, lift, wipe, step, pause, lift, wipe, step. The electric hum coming from the piss-gray light provided a tribal chorus to the figure's ritual, and soon enough it had reached its destination: the door on the left.