I am a commercial interior designer (by day). I design office buildings. I have found in a commercial setting people are much more open to using color. In peoples homes, most play it safe by adding pastels or minimal color. Think about the last time you have been to a retail store or building lobby. What stands out to you when you enter the space? The simpliest and cheapest impact is color, paint specifically.
You can add a deep, saturated color in a space even if it is small. Where is the key. Having a single, impactful wall sets the tone without being over-powering.
Neutrals are good, but add a splash of color with it. I am obsessed with henna red, and shades of browns and oranges in my home. The first thing I did when I moved into my house was paint a deep brown in my entry way that runs into the living room. I was bored with the white walls from apartment living for so many years. It is a single wall and I left the rest of the living room with white walls. It sets the tone for the room without being overpowering. It serves as a nice backdrop for my entry table, and my TV and pictures on the walls. I have brown sofas and mahagony wood. It would be deadly with all of these browns, tan carpet, and tan stone table. I added henna red pillows on my sofas and it added just the right punch. If I get tired of this color, they are easy to replace with new ones.
I have a grouping of pictures on my living room wall. I was getting tired of all of them, but couldn't seem to find the right pictures to replace them, at least the ones I could afford. I changed out three of the pictures that were just okay, and framed pretty scrapbook paper in the original frames. (See my post Cheap Art, Big Impact.) I used the same color combination in my living room to tie it all in. I feel it is just the right touch.
Choose a color that has more "gray" in it than a true color for a wall. True colors are great for clothing, paper, and more, but when it comes to walls it will look juvenille and unsophisticated. You can start with your favorite true color, blue for instance. Then look at the section that is more gray. Big difference, but still will look lovely.