Get this look by doing a base coat in a light color. Roll a darker colour overtop - while the paint is still wet, use a dry brush to brush off and smooth the paint out - exposing the colour underneath.
There are many different painting techniques you can use on your walls or any surface to create interesting textures and effects. Have a look at some of the techniques here: http://www.diynetwork.com/how-to/skills-and-know-how/painting/how-to-create-decorative-paint-techniques
Like the look of this in a bedroom with turquoise, gold and black color scheme. Faux Painting with Metals and Patinas
How to Create a Faux Fabric Effect with Paint via This Old House
Faux Painting For Dummies: Faux Painting Techniques: Ragging , Frottage, Smooshing, and Sponging
Decorative paint techniques!- This red is my favorite- glazed or washed, but it looks like something that is also done with natural plasters in less intense colors.