If the stairwell does not get a lot of light then stay away from dark colors like teal and navy. Either go with a light neutral like neutral light brown or white. Or go a bit bolder - choose a piece of art with plenty of yellow in it, then choose a paler yellow wall color to look good with it. Is your house contemporary, transitional, colonial or?? A print like this Van Gog has yellow and also the navy that you have elsewhere in the house. https://www.vangoghgallery.com/catalog/Painting/53/Caf%C3%A9-Terrace-on-the-Place-du-Forum,-Arles,-at-Night,-The.html

Can you post a photo of your staircase?

Since you said bold, I’d go with wallpaper too

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Use a color you are already using elsewhere but really we need to see your space and how the stairway relates to the rest of the house.

Wallpapering a staircase can be a difficult job because of the climbing and the reach sometimes needed. My dad did his hallways and it was hard. A bright piece of art is easier to hang, and you just need to get the right toned-down yellow to give it life. A bright color is good for a darker space, and you are already using yellow elsewhere. Repeating colors is good. Another one is Noon Rest by Van Gogh - a nice picture for going up the stairs to bed, maybe.

Wallpapering seems daunting. Here are two pics of my staircase. (Second one won’t post, but there is a small window at the top of the stairs) Until I can replace them, I plan to paint the wood rails Benjamin Moore, Kendal charcoal, which is the same color as our kitchen cabinets. To the right, when you walk in is the staircase and to the left an open living room with these curtains hanging. (See link below) To give an idea of my colors. I have lots of green in the hosue as well, its my favoite!

https://www.houzz.com/products/signature-everglade-teal-blackout-velvet-curtain-single-panel-50x96-prvw-vr~132701761?lid=65582148

What's your favorite color? Chose a version of that which goes well with your other colors. There is no wrong choice.

I have lots of yellow accents and would be open to a yellow wall. Was also thinking something like chartreuse, but worried that might be too bold!

Get large samples of a chartreuse (BM Chartreuse would be a good place to start) and the sort of yellow you are envisioning from https://samplize.com/ This should help you decide on which direction you prefer. What sort of yellow are you envisioning btw...creamy,sharp,pastel? Myself, I'd likely go with a rich chartreuse shade. Not because it is more 'bold' but because I just like it better. Good luck, hope you keep us posted.

I would prefer the chartruse or lime green over yellow, if you want a bold statement.

Benjamin Moor Dark Royal Blue 2065-20.

https://www.benjaminmoore.com/en-us/color-overview/find-your-color/color/2065-20/dark-royal-blue?color=2065-20