Colors
Play-Doh, introduced in 1956, was originally available only in off-white. By 1957, the primary colors yellow, red and blue became available and as of 2011 it also comes in neon and pastel colors. Silly Putty, which bounced onto the market in 1949, comes in its original pink-like color, as well as a brighter pink, blue, yellow, and orange. Three special Silly Putty colors change, chameleon-like, from purple to pink, orange to yellow, or forest green to bright green. In conjunction with its 50th anniversary, Silly Putty introduced a metallic gold color.
Texture
Both Play-Doh and Silly Putty can be molded easily, but they feel and act very differently. Play-Doh holds its shape, making it suitable for sculptural work. Don't bother trying that with Silly Putty because it will collapse on itself. But Silly Putty's elastic properties allow it to stretch to outrageous lengths or, if pulled apart quickly, snap in two with a clean break. This same property allows it to bounce.
Effect of Air
Anyone who has left Play-Doh out of the container overnight can tell you what air can do to the substance; what was once soft and malleable becomes hard and brittle. (Adding water a drop at a time or wrapping the Doh in a wet paper towel can return it to its original texture.) Silly Putty, on the other hand, is not affected by air. It comes in a plastic egg that can be snapped open with a slight squeeze and snapped shut again for safe keeping.
Accessories
Since Silly Putty doesn't hold its shape well and doesn't respond well to tools, it is best used with bare hands. Play-Doh, however, can be manipulated with plastic knives, poured into molds, or run through toy pumps that force the Doh into various shapes. Play sets use these tools and Play-Doh to create anything from cartoon characters to teeth for a most unfortunate dental patient.