A Note About Color Classification in Tomatoes
The way tomato colors have been described has changed through the years. We use the most common current color nomenclature, but even that is in flux, as noted below.
In general tomato color is determined by a combination of skin color (clear or yellow) and flesh color (made up of a variety of green, orange, and red pigments). Blue highlights, skin stripes, bicolor flesh, and culturally-dependent color variations confound our ability to cleanly classify everything, but we broadly categorize tomatoes by their combination of skin and flesh color.
Some variety distinctions are made by skin color, of which clear and yellow are the common variants. Yellow skins can vary considerably, especially due to cultural influences, and a yellow skin which is almost clear in one garden may be very yellow or even amber in another. This leads to some confusion in describing tomatoes, particularly for growers who don't have experience identifying skin color and its variability.
Recently, blue tomatoes have been introduced by crossing wild tomatoes and relatives into modern tomato stock. These have anthocyanin in the skin, not uniformly distributed, and principally in the parts of the fruit exposed to sunlight. Anthocyanin is the same pigment as in blueberries, blackberries, etc., and although it is a purple pigment it can look anywhere from red to blue in plant material depending on how and where it is distributed in the tissues. There is no strong consensus on how to classify these blue tomatoes, but normally it is added to the color description, as in "a red tomato with blue shoulders."
The "common" red tomato is composed of red flesh (famously supplied by lycopene pigments) and yellow skin. Orange pigments may or may not be present in the flesh, but green and darker colors are generally absent.
Pink tomatoes have red flesh, as in red tomatoes, but clear skin. Historically these were often called purple, but that's considered incorrect now.
Purple tomatoes have darker overtones in the flesh and are often considered a new development, even though historical and heirloom varieties of these are common. The darker colors may actually be green pigments or other colors, but it is often hard to tell. The term black is inconsistently used to describe these tomatoes, and although it would seem to be more commonly applied to darker flesh colors, that is not always the case.
Sometimes a special distinction is made for purple tomatoes with yellow skin, and these are called brown. Consensus is not strong, though, and this classification is inconsistently applied. Brown tomatoes are more likely to be called black than purple. I've seen at least one definition that designates both purple tomatoes and brown tomatoes as subsets of black, the former having clear skin and the latter having yellow. This is as clear a way forward as I any I've heard.
Going the other direction, tomatoes that lack the red color but have large amounts of orange pigments in the flesh (often carotenes) are usually called orange, particularly if they have yellow skin. Yellow skin, though most common, is not a requirement for orange categorization.
Orange tomatoes with smaller amounts of pigment are sometimes called gold. There is really no clear line between orange and yellow tomatoes—varieties can be found along the entire spectrum from bright orange to pale yellow.
The term yellow seems to be primarily reserved for lemon yellow tomatoes, usually with yellow skin, but the gold designation is common here as well, and there are some darker yellow tomatoes commonly designated as yellow.
White tomatoes have clear skin and pale yellow flesh. No tomato is completely white, though breeding efforts have been directed at making white tomatoes as light as possible. I usually refer to white tomatoes as white/cream, and they tend to be even more cream colored (not necessarily yellow) in my test gardens than other parts of the country.
Green tomatoes don't lose their chlorophyll as they mature, and hence remain green even when fully ripe. Most green tomatoes that are available have yellow skin, which both enhances the "greenness" of the color and provides a color break that helps gardeners tell when they are ripe, since the yellow doesn't generally develop in the skin until the tomato is ripe, and that yellow color can get really dark under some cultural conditions.
There are, however, some green-when-ripe varieties with clear skin, and these have a particularly "unripe tomato" look. Some of these have the clarity of skin in the name, such as in Tom Wagner's "Verde Claro," but so far there is no separate color designation for these tomatoes except "clear green."
Tomatoes where the pigment is not evenly distributed through the fruit, or where pigments vary in different parts of the flesh, are called bicolor. Theoretically there are many possibilities here, but in practice only the red/yellow combinations are commonly called bicolor, and other combinations where there is clear variation in the color of the flesh are both rare and uniquely defined.
Striping in tomatoes is usually limited to the skin, and it's unclear whether tomatoes where the color variation also seems to affect the internal flesh are actually better characterized as striped bicolor, with two unrelated phenomena occurring in the same tomato. Stripes can occur in a wide variety of combinations.
Speckling of a secondary color on the outside of the tomato is commonly treated the same as incomplete striping. There are many variations of color distribution on tomato skins, but they are usually limited to longitudinal markings, with the notable exception of blue tomatoes.
There are many other characteristics that can change the look of tomatoes, including fuzzy skin and odd markings, but these don't usually alter the conventional color classification.