Three colors used in that fashion seems like sensory overload to me. But I'm not a fan of accent walls so take that FWIW.

Rules for the road might be that the use of an accent wall in a bedroom would be the focal wall and be behind the bed.

Another one would be and I'm not sure that it totally a rule, but it's usually good to repeat the element elsewhere so that it maintains consistency. I could see this one broken if it's just the bedroom, but if it were in the living room, then I would want to see it repeated elsewhere in the house.

I think you should post a pic, it could be sensory overload with a peaked ceiling because it might be too many architectural elements in one spot.

I think that it would be very tricky to get 3 shades of green, some more yellowey, and some grayer to look good together.

Here is the floor plan. It is an odd room, you walk in the door from a small stair landing and first go through a short "hall" though about 18 inches longer than what is in the drawing.) Closet in front of you, to your right the bathroom to your left an opening to the room. The room has a vaulted peaked ceiling that follows the roof, but it flattens at the top (flat part runs from where you walk into the room to the wall with the window, probably 6 feet wide.) The faint outlined rectangles are the bed and two dressers. The furniture is all stained medium brown. The decor is simple - either medium blue bed bedding(we have now) or a teracotta color (could never find nice stuff we could afford to pull off that look) but no crazy patterns with all the wall color.

The colors I am considering are pretty similar, so it would not be a striking accent (two yellow-greens - BM pale avocado 2146-40 & castleton mist HC-1, two gray-greens BM Mesquite 501 and Dried Parsley 522 & one paler green BM rainforest dew 2160-50.

In our old place, we used BM Dill pickle on the walls and something lighter on the angles/ceiling (that was a much larger room with lots of drama so a more intense color worked.)

I was thinking of one of the more yellow greens on the walls, a gray green on the east wall where the bed is and a lighter yellow green on the angles and flat ceiling (it could even just be a slightly lighter version of the yellow green on the walls.) The other question is the "hall" that leads into the room. I thought that could be a complimentary gray with a hit of green which would lead to some mild punch in the room.

Opposite the walk through from the hall to the room is a bathroom. It is very mellow - putty polished large format tiles on shower walls, calcatta marble hex on the floor. So I though the grayer walls in the "hall" would be a better transition to the bath (which will probably be some very neutral shade of white, gray, putty or taupe) than the more vibrant greens.

Insane or interesting? Better ideas? I can scrap the idea of an accent wall all togehter, but much of the house paint is pretty mellow so we thought we could have some fun in here.

Here is a link that might be useful: photos of bedroom wanting accent wall

It sounds like too many colors. I personally think there are too many angles in the room that adding multiple colors would be jarring. Jarring is not really a good idea for a bedroom where you might calm and restful. How about all the room in the yellow green and the accent wall behind the bed in a grayer green? Then for a little fun, maybe a different color(coordinating) for the bathroom?