How do I repaint a recessed bookcase to have a beach theme?

I would either use sand color on the outside and teal or sea foam green on the back walls. Or you can get a nice wallpaper for the back walls.

I don't think it matters what color you paint it. What matters more is what you put on it to carry out your beach theme. Here's some ideas: https://www.pinterest.com/pin/98657048070351905/?lp=true

I would love to see a picture when you are done! Please! This is a great idea. How about a mural type ..very muted with sand,water colors..sky colors,as I am thinking..muted so as not to take away from your beach displays...shells, glass,sand in bottles etc. please post picture! On this post because I would probably never find it again! 😳🤪

I checked "explore projects" then "walls" then "wall art" and found this sea scenery for you. I think it might give you some ideas of your own maybe. You could add a shelf or two also and set more shells on them, but anyway, there are more of them if you put "seashells" in the search box in that area of wall art. Here is one of their ideas: https://www.hometalk.com/diy/decorate/walls/beach-shells-canvas-a-quick-diy-project-29380211

Beach Shells Canvas - A Quick DIY Project