Modern Ultramarine Blue
This color is a rich royal blue that comes in a handful of subtly different varieties. It's pigment code is PB29, meaning if you turn over a tube of paint, PB29 denotes that ultramarine is a pigment used in it. To make things a little confusing, PB29 can describe slightly redder variations of the color (meaning more of an indigo blue as opposed to a deep middle blue) as well as the natural Lapis Lazuli, which in modern paints is a very different experience than regular ultramarine. However if you're dealing with old school Lapis, the manufacturer will go out of their way to tell you so, as it is an expensive pigment and you will likely notice its enormous price as well. It's worth noting that it's difficult to find a bright blue genuine lapis paint due to the expense and difficulty of acquiring the finest quality grades, and the genuine lapis paint on the market that we've tried tended to be fairly low chroma compared to modern ultramarine.
Explore Ultramarine Blues
Sometimes the regular Ultramarine Blue a brand has will actually be what some brands call Ultramarine Blue Green Shade.
Ultramarine Green Shade?
Paintmakers vary a lot in how they apply the term "green shade" to ultramarines. We could take it to mean "not the red shade" or the slightly-less-indigo-one.
However manufacturers get creative and as an example of this, Rublev uses the term Green Shade to denote both the hue of the pigment and the binding oil for their ultramarine. See Rublev Ultramarine Blue (Green Shade). In the image above, Rublev's Ultramarine is second from the right. Most brands denote Green Shade to mean what we call regular ultramarine and separate it from the Ultramarine French variety. We'll have to do more testing across mid-tier and student brands to say much more about how this term is applied. It's safe to assume (most of the time) that green shade means regular ultramarine, however it's always good to check with the manufacturer.
Ultramarine Blue vs. Ultramarine Blue French?
In short, Ultramarine French is usually- but not always!- more toward Indigo than a true blue. Sometimes people describe the more indigo shade as being "redder." Unfortunately there is no way to tell by looking at just the pigment code as they share the designation PB29.
It's not always clear what the difference is when a person is standing in an art materials store or looking at swatches online. Furthermore the name space is a bit confusing because sometimes a brand will name Ultramarine regular as Ultramarine Light.
What About Ultramarine Blue Light and Ultramarine Blue Deep?
Sometimes Ultramarine Deep is the same as Ultramarine French. Unfortunately there is no tried-and-true way to determine the leaning of the pigment without trying it, since each brand varies.
We noticed that a number of European brands went with the naming scheme of Ultramarine Blue Light to denote the regular, less-purple middle blue shade, and used Ultramarine Deep to denote the more indigo (red shade) of the pigment. Here are a few Ultramarine Blue Deeps on Paint List.
A couple of European brands combined the terms Ultramarine Blue Light with the name French. Blockx has a French Ultramarine Blue Light, which is PB29. And then there is Old Holland, which does something totally different. Their French Ultramarine Light Extra (combines the terms ultramarine light and the word French)-- names a color blend that contains both ultramarine PB29 and cobalt blue PB28.
And then there is Schaal, who actually is French, who has Bleu outremer foncé. Foncé means deep.