Craig of Newmarket writes, "I want to paint our master bedroom dark red. My wife is freaked out about it and is concerned she won't be able to relax in the room. Can this colour really affect her that much?"
Craig, there are many theories about how colour may or may not affect people physically, emotionally and psychologically, but because the psychology of colour is not yet completely supported by firm scientific data, the theories may be considered anecdotal in nature. Regardless, I think your question is worth exploring.
What I know for sure is that like selecting your child's name, picking colours is a very personal thing and can not only mean different things to different people, but also is said to impact individuals in very different ways. Much like exposure to certain smells and odours, perceptions of colour are greatly influenced by personal life experiences as well as an individual's cultural upbringing.
That said, fear of using red particularly a dark one, can be driven simply by a dislike for or discomfort with any colour deemed too intense. You may want to consider other colour families and choose equally intense hues as potential alternatives in order to see if it's simply the intensity of the colour that is in question, or the colour itself that your wife is opposed to.
Moreover, no matter how trivial it seems, the names of colours and how we choose to categorize them (for example, one grey is bluer than another) can also impact an individual's ability to see a colour for what it is. I may have told the story before of my clients who selected a colour called "Maid of the Mist" primarily because it was the location of their engagement. Regardless of whether or not the colour was their first choice, it's name sealed their decision and as such determined many of their subsequent colour and decor decisions.
When selecting colours with clients, I have a tendency as a decorator to use phrases like "this beige is pinker than that beige." I have learned over the years to choose my words carefully since the mere mention of the word pink sends many men running from the room. I once had a client request that I not refer to the word yellow in any conversation with her husband for fear that he would immediately eliminate even the notion of using that specific paint colour.
In the interest of finding a red both you and your wife can agree on, consider searching out an earthy tone - something that has brown undertones, rather than selecting a true primary red or even worse, a blood red. We don't want you to end up with colours in your home that bring to mind the movie "The Shining". Have a look two examples in what is quickly becoming my new favourite colour collection, Sherwin Williams SW6299 Aged Wine and SW0072 Deep Maroon.
Before we discuss the potential psychological impacts of colours, I caution you to think about the furnishings and linens that are in your bedroom. If you decide to use a dark red paint in your bedroom, I would ensure that you introduce whites sparingly. For example, white sheets or window sheers may get a cast of pink on them from light reflection when coupled with intense red walls.
At the risk of generalizing and over-simplifying colour psychology, red is often considered to be a stimulating colour that evokes passion and intensity. Perhaps not a bad colour for the master bedroom! However, for some people red is an angry colour and is often believed to increase heart rates and blood pressure.
According to feng shui principals, "...although red elicits a feeling of warmth and richness, too much red can be over-stimulating and cause tension, anxiety, and even aggression." (http://www.feng-shui-and-beyond.com)
If we are to believe the popular colour psychology tenets often referred to by design professionals, you may find that a more restful colour for your bedroom is a spa-like blue. Certainly "spa-like" often implies watery, softer colours, so while your wife might prefer this, it may not be something you're willing to consider.
I would argue that darker, more intense colours could often make a room feel cozy. While this may be the effect you want a colour to have in your space, knowing what is at the root of your wife's aversion to red walls may help you determine if your colour choice will have the same effect in the room for her.