Quinacridone: A large family of modern, moderately saturated and highly colorful pigments, repeatedly noticed in chemical research since 1896, but not recognized as useful pigments until 1955 (by W. Struve at DuPont, who also developed economic methods of manufacture). The first quinacridones were marketed in 1958 as automobile colorants and artists' paints, which were promptly adopted by New York abstract expressionist painters. The available hues range from golden yellow (PO49), through reddish orange (PO48), middle red (PR209), coral (PR207), red (PV19), rose (PV19 and PV42), magenta (PR122, PR202), maroon (PR206), and a dark reddish violet (PV19). Nearly all quinacridones have excellent lightfastness ratings in watercolors.
"Hue" Paints: To conform to the ASTM labeling standards, manufacturers must also use the designation hue for a paint that is named with a pigment common name but that does not actually contain the pigment. For example, a paint named Manganese Blue must contain the pigment "Manganese Blue, PB33," and if it does not, it must be called Manganese Blue Hue. Every paint manufacturer I know of does not respect the letter of this standard, especially for historical color names —carmine, madder, sepia, indigo, van dyke brown, gamboge, emerald green, and any color name with sienna, umber or earth in it.
Ultramarine and French Ultramarine: Originally, Ultramarine Blue was mined as Lapis Lazuli and was more expensive than gold. Since the early 19th Century, Ultramarine was available in a synthetic form, which has the same chemistry, but a different crystalline structure, and is quite economical compared to the original Lapis Lazuli. It’s often chosen as a mixing blue because it’s not as overpowering as Phthalo Blue can be, and it’s unique in that the particles “flocculate” – or clump together – creating interesting effects for watercolorists.
A question artists often have regards the difference between the standard Ultramarine and French Ultramarine. Both use pigment identifier PB29, but French Ultramarines will have a larger particle size, and the higher silica content causes the color to lean slightly more to the violet range, whereas Ultramarine (not French) will have smaller particle size and poor silica content and tends more toward the green. Depending on the settings of your computer monitor, you should be able to get an idea of the difference with the examples below.
Ultramarine 
French Ultramarine
As far as the "original" Ultramarine, Lapis Lazuli, hue can vary widely based on where it is mined and how it is processed. Much of the time there are enough other minerals still present to give it a grayish cast -- when it is refined to the vibrancy of the synthetic Ultramarine, the process is so involved that such high grades of Lapis Lazuli pigment are very expensive.
Fun Fact: Like most colors, ultramarine pigment takes on a different appearance depending on the binder it’s mixed with. French Artist Yves Klein worked for many years to develop a proprietary binder that would enable ultramarine to retain the vibrancy of color that the pigment has in dry form. The color that resulted is known as International Klein Blue.
Color Wheel
Lee H. has gone down the wonderful rabbit hole known as Handprint.com. Here are links to some of the many informative PDFs.
Artist's Color Wheel
Artist's Value Wheel
Color Palettes
Because we were talking about color palettes on Tuesday, I thought I would include these articles by Jane Blundell. It's a start., if you are trying to limit your color choices for plein air or just sanity in general.
Jane Blundell, The Ultimate Watercolor Mixing Selection
Working with a Split Primary Color Palette
Minimal Watercolor Palettes