Roald Dahl used only pencils with yellow casing to write his books. He had 6 sharpened pencils

The majority of pencils made in the US are painted yellow.[44] According to Henry Petroski,[45] this tradition began in 1890 when the L. & C. Hardtmuth Company of Austria-Hungary introduced their Koh-I-Noor brand, named after the famous diamond. It was intended to be the world's best and most expensive pencil, and at a time when most pencils were either painted in dark colours or not at all, the Koh-I-Noor was yellow. As well as simply being distinctive, the colour may have been inspired by the Austro-Hungarian flag; it was also suggestive of the Orient at a time when the best-quality graphite came from Siberia. Other companies then copied the yellow colour so that their pencils would be associated with this high-quality brand, and chose brand names with explicit Oriental references, such as Mikado (renamed Mirado)[46][47] and Mongol.[48][49]
Not all countries use yellow pencils. German and Brazilian pencils, for example, are often green, blue or black, based on the trademark colours of Faber-Castell, a major German stationery company which has plants in those countries. In southern European countries, pencils tend to be dark red or black with yellow lines, while in Australia, they are red with black bands at one end. In India, the most common pencil colour scheme was dark red with black lines, and pencils with a large number of colour schemes are produced by various companies.
Pencils are commonly round, hexagonal, or sometimes triangular in section. Carpenters' pencils (see below) are typically oval or rectangular, so they cannot easily roll away during work.
Notable pencil users

Thomas Edison had his pencils specially made by Eagle Pencil. Each pencil was three inches long, was thicker than standard pencils and had softer graphite than was normally available.[21]
Vladimir Nabokov rewrote everything he had ever published, usually several times, by pencil.[21]
John Steinbeck was an obsessive pencil user and is said to have used as many as 60 a day. His novel East of Eden took more than 300 pencils to write.[21]
Vincent van Gogh used only Faber pencils as they were "superior to Carpenters pencils, a capital black and most agreeable".[21][50]
Johnny Carson regularly played with pencils at his Tonight Show desk. These pencils were specially made with erasers at both ends to avoid on-set accidents.[51]
Roald Dahl used only pencils with yellow casing to write his books. He had 6 sharpened pencils ready at the beginning of each day and only when all 6 pencils became unusable did he resharpen them.[citation needed]
Types

By marking material


Coloured pencils


Promotional pencils
Graphite pencils
These are the most common types of pencils, and are encased in wood. They are made of a mixture of clay and graphite and their darkness varies from light grey to black. Their composition allows for the smoothest strokes.
Solid graphite pencils
As the name implies, these are solid sticks of graphite, about the diameter of a common pencil, which have no casing. They are often called "woodless" pencils. They are used primarily for art purposes as the lack of casing allows for covering larger spaces easier, creating different effects, and providing for more economy as the entirety of the pencil is used up. They are available in the same darkness range as wood-encased graphite pencils.
Charcoal pencils
They are made of charcoal and provide fuller blacks than graphite pencils, but tend to smudge easily and are more abrasive than graphite. Sepia-toned and white pencils are also available for duotone techniques.
Carbon pencils
They generally are made of a mixture of clay and lamp black, but are sometimes blended with charcoal or graphite depending on the darkness and manufacturer. They produce a fuller black than graphite pencils, but are smoother than charcoal.
Coloured pencils, or pencil crayons
These have wax-like cores with pigment and other fillers. Multiple colours are often blended together.[52]
Grease pencils
They write on virtually any surface (including glass, plastic, metal and photographs). The most commonly found grease pencils are encased in paper (Berol and Sanford Peel-off), but they can also be encased in wood (Staedtler Omnichrom).[52]
Watercolour pencils
These are designed for use with watercolour techniques. The pencils