Hallways are usually dark. I wouldnt put a dark color in there. I agree, louvered doors would be a better option than what you have. Keep the hallway light and bright. I do think pretty art work, and a nice rug (light bright and colorful), would distract from the vents. Its not unusual to have an attic opening in your hallway, since that is one of the best places to put it. Paint it all the white of the ceiling. The vent in the wall over the door, paint the same color as the wall, so it just blends right in.

Try painting the door, its trim and the wall above it black, thinking black would make the vents disappear. How about taping it off to make large stripes, which should make the area look larger. Go with any two colors that work for color scheme you will have going on.

Where does the doorway that's closest to it lead? Is it frequently used? Can't tell if there would be enough room for one of these (altho a 3 panel might work best). If it doesn't block the door on the right, it could just be sitting on the floor. But if there is not much room to pass through that door, you could attach one side with hinges to the sidewall and then maybe just a hook and eye on the other side to hold it in place, but it would easily swing open to access the closet behind.

Before someone comes along and says it will block the air vents, it won't. It wouldn't be installed tight up against them and air flows like water....anyone trying to weatherproof their homes can testify to how easy it is for air to flow.

Lots of choices. These are all from Wayfair.

You could also look at peel and stick murals that would cover the whole thing. The vents would be a little labor intensive or look for a pattern that could disguise them. Or paint them a color/s to blend in. I just googled peel and stick murals for closet doors.

I’ve never seen a solid door McGuyvered-up like that before. Jerk those doors out and spring for new louvered doors, for sure.

Paint everything else some shade of white. Put a pretty light-colored runner down.

I can’t see the ceiling light. Is it an old-fashioned boob light? Replace it with something more charming, something that might block the view of the attic hatch a bit. Make sure it’s centered and maybe move it towards the attic hatch.

The doors lead to a closet with the HVAC system. There’s no room to put a room divider.

You could definitely replace the doors with a louvered door for venting, but I do love the idea of a black door there. You can spray paint the vents after cleaning them. I personally might try to add personality to the current doors–add a frame, trimming the edge, then glue and nail wooden slats, paint it all black. You could wallpaper or stencil the hallway, and it would look great. The ceiling–I would leave it white, a fresh coat of paint. Is there some kind of insert for the ceiling? Paint it all to blend in with the white ceiling.