Our company is appropriately named. Color IS good!! ; )
I do a lot of paint color selections for clients. It is an intimidating task for people to not only select good color, but to know where to stop and start the paint...what finish to purchase, etc...
That's where I come in...So many colors can be neutrals...that's the joy of it! I feel like when you add the right depth and value of color to a space, you can really make your house a home. It makes THAT big of a difference...
A super general rule of thumb...I try to select a "main color" for a home. It can range from all sorts of tans, to greens, golds, etc...if you "deepen" your main frame of reference for the darker accent colors, it works better. For instance, if you have a warm coffee color on your walls, then if you add a deep barn red it has less contrast and is more appealing. Again, sometimes the main thing you're going for is contrast, so there are no set rules...
As far as stopping and starting color, I try to never end paint on an outside corner...again, that's a generalization, but I think it feels unnatural and "choppy" to do that. If you "connect" the rooms in a real intentional way and end color on inside corners when possible, I think you'll really enjoy the result.
So when you're doing an "accent wall" consider when you're walking into the space doing the two walls that "draw you in" instead of just the "end" accent wall. It can really make an impact in the room...
Most paint companies make "samples" of all the colors. I like to recommend that my clients paint on foam core boards so that they can move them around the house to view with furniture, art pieces, and to see in other lighting situations...rather than to make "marks" all over the walls making it hard to cover later when the "real color" has been applied...
Generally speaking, I recommend an eggshell finish or a flat enamel. Each company has their own types of finishes, but I like it to have little to no sheen with the ability to be washed...depending on the space of course...I think dark colors look much better when they're not shiny. It's no longer critical to use semi-gloss paint in bathrooms and kitchens...a lot of companies have really improved the washability of their paints...
Well...hope some of that is helpful to you as you step outside your white and/or tan boxes...Color IS good...it's GREAT in fact! ; )
So many people feel "stuck" with their white walls. They are afraid that if they change the color it won't give them options, but like you said, Kim, there are a lot of colors that still act as a neutral, allowing you to put almost any kind of furniture or decor in the space.