Pantone's (very fast!) reply, which was signed off for publication here by the very friendly tech rep.
Pantone has many different color sets that are designed to specify and communicate color across different industries. The Pantone Plus Series is based on graphics/printing ink and is the well-known Pantone Matching System (PMS) that has been around for 50+ years. These are the colors that are specified with numbers and a suffix such as ‘C’ or ‘U’ which specify the type of paper the ink is printing on. For example, Pantone 100 is the ink color and Pantone 100 C is this printed on Coated paper. There is also Pantone 100 U which is the same color ink but printed on Uncoated paper. The same Pantone color printed on coated and uncoated paper will have quite a different visual appearance. Although there is a variance in ink film thickness, the majority of the difference is attributed directly to the reaction of the ink to the paper.
These colors are all specified with a number only and the suffix for paper type and print process. The exception being the 18 Pantone Basic Colors (base inks) that are used to mix the rest of the colors. These are colors such as Pantone Yellow, Reflex Blue, Black , Green, etc. The other exception is we have colors that fall in the ‘Gray’ and ‘Black’ colors that are named as ‘Warm Gray’ or ‘Cool Gray’ or ‘Black’. These also come with a number association as there are many different shades/hues of these colors. So that is why there is Pantone Cool Gray 1 C. There is 11 Cool Grays and 11 Warm Grays and 7 Blacks.
The other commonly used color system is our Fashion Home + Interiors guides (commonly referred to as FHI). These guides are based on specifying textiles. These come in two formats, Paper (TPG) and Cotton (TCX). The Cotton is a dyed cotton fabric swatch of the colors and the Paper is a lacquer paint/coating on paper. Depending on the product you are working with would determine which guide you would want to visually see the color on, fabric or paper. These are specified as 18-1443 TPG for the Textile Paper guides and 18-1443 TCX for the Textile Cotton guides. So the color is 18-1443 and the TPG or TCX specifies which format of textile guide these are found in. These colors are a separate set of colors to the Pantone Plus Series.
These colors all come with a number format of two digits hyphen four digits and the suffix of TPG or TCX. Being as these colors are separate from the graphics/ink guides and were developed later they have been given ‘names’ to go along with the number specification. This is why colors such as 18-1443 also has the name ‘Redwood’.
I hope this has given you some insight and clarification into why some colors have ‘names’ and while others do not. One thing to keep in mind is we always recommend associating the number and suffix as this will accurately allow accurate color communication. Please let me know if you have any questions.