Let's get to the root of the problem. First of all- there is nothing inherently wrong with a two- color pallet. Do you really want more color, or do you simply want a more beautiful, interesting room? I find that what is more commonly the issue is a lack of pattern and textural variety.
Start by taking a look at your room from a perspective of pattern. How many different patterns do you have? Are they varying sizes? In a typical bedroom, I would suggest you have at least three different scales of pattern. For example- you can have a medium size pattern on your bedding, a larger, bolder pattern on your rug or wallpaper, and a small pattern on your window treatments. These patterns do not have to have a lot of color in them- they could all be shades of the same color and still look great.
Next look at your room in terms of texture. What different varieties of texture are there? Do you have any rougher textures like a rattan or jute? Increase your textural variety with different fabrics- accent pillows are an easy way to do this. They can be covered in anything from patent leather to fur. Take a look at your walls and ceiling- are they all drywall? Consider wood paneling, textured wallpaper, or a beamed ceiling. Replace your window treatments with a combination of woven Roman shades and silk panels. Add plants. Greenery- whether faux or real- is a perfect way to add textural variety to a room. Something rough, something nubby, something smooth- textural variety will add interest and beauty to your room like nothing else.
When you finish this exercise, do you find that you still need more color? If so- write me back :)