Ragging and frottage are two simple paint techniques that add color as well as texture to walls. Ragging is the technique of applying paint (or removing it), using a cloth rag and leaving the pattern of the fabric behind. Frottage involves applying color to a surface then using crinkled plastic or paper to create effect. You can use the existing wall color or paint the wall a new color before choosing a paint color that you want to use with the ragging or frottage techniques. You may want to use latex gloves for either of these techniques, as they can be very messy!
If you want to use ragging on your walls, first prepare a 1:1 mixture of wallpaper paste and latex paint. To apply color, pour the paint mixture into a paint tray and dip scrunched-up fabric into the paint. If you want to use the technique of "ragging off," simply apply the paint mixture haphazardly (but with an even coat) to the wall. Then dab scrunched-up fabric onto the wall's surface to remove some color.
If the fabric gets too saturated with paint, be sure to take time to wring it out occasionally. Otherwise, you might find that your ragging pattern is sparser in some areas and more intense in others.
Frottage is similar to "ragging off." Apply an even layer of paint to the wall. Then, take paper or plastic that has been crinkled or scrunched, and place it onto the freshly painted wall surface. While the paper or plastic is still touching the wall, crinkle it further. This will aid in the pattern appearing smoother and more natural. If you find that you need more color, give the wall another layer of paint and repeat the process. Dab and crinkle the paper or plastic as necessary. You will find a method that works best for you and the look you are trying to achieve.