It sounds so easy: pick a color and reeeeally commit, but not so fast. There are a few tricks that will help you make your monochrome look chic and classy, not overwhelming.
Texture is essential
When you're limiting your color palette, it's so important to give your space some interest in another way. Texture breaks up the large swaths of color and helps your room look chic, not boring.
Explore a range of shades
See how this room picked one color to work with (grey) and then mixed it up with varying tones and shades? That's why it works. Overdoing it with the same shade of the same color will just overwhelm. A nice mix makes it look cohesive but interesting.
You don't have to do the whole room
If you don't want to go whole hog, that's okay. Try your hand at a vignette or display a similarly-colored collection. Nothing says your monochrome has to be all-encompassing. Try a little and, if you like it, scale up from there.