Color Comparison: Phthalo Green (PG7) vs Cobalt Turquoise (PG50) for Mixing Spring Greens

I’ve always found Phthalo Green Blue Shade (PG7) to be the most useful mixer for bold, bright, new, spring shoots. Compared to blues, even the very bright and greenish Phthalo Blue Green Shade (PB15:3), Phthalo Green consistently makes cleaner, brighter greens. In my post Mixing Watercolor Greens for the Foliage of the Northeast, Season by Season, I recommended PG7 and Lemon Yellow (PY175 or PY3) for the best spring green mixes. After doing a tutorial with Paul George, I began mixing up spring greens with another color: Cobalt Turquoise (PG50). So how do these colors really compare?

DS Phthalo Green (PG7) vs SH Cobalt Turquoise (PG50)

If I were to name each of these concentrations, I would call them:

  • PG7: Green Agate, Jungle, Fresh Mint, Spa
  • PG50: Turquoise, Tropical Sea, Horizon, Aqua

In a typical Color Comparison, I compare two colors that appear very similar in hue, and try to find subtle differences in properties or mixing. In this case, the colors are obviously different. The hue is different – green vs turquoise – and the two colors could not be more different in properties: Phthalo Green is transparent, smooth, and staining while Cobalt Turquoise is opaque, granulating, and lifting.

Going by hue alone, I would think to use Phthalo Green for the Northern Lights and Cobalt Turquoise for the clean, clear waters of pristine seas or lakes.

But what happens when the colors are mixed?

Mixing Yellow

The surprising finding – and the reason I wanted to make this post – was how similarly these two colors mix bright, spring greens!

Spring green mixes with Phthalo Green (PG7), top row, vs. Cobalt Turquoise (PG50), bottom row.

In the page above, the top row is mixes with Phthalo Green, and the bottom row is mixes with Cobalt Turquoise. The leftmost column mixes both with Hansa Yellow Light (PY3), the middle column mixes them with Imidazolone Yellow (PY154), and the rightmost column mixes them with Nickel Azo Yellow (PY150).

I was shocked by how similarly Phthalo Green and Cobalt Turquoise could mix with all three yellows! They are much more similar than the greens mixed by, say, Phthalo Green and Phthalo Blue. There are differences in texture (Cobalt Turquoise mixes have granulation) and in range (Phthalo Green mixes can get darker if you mix in more green), but in terms of hue they are shockingly similar.

I had always assumed that I need Phthalo Green in my spring palette in order to make those bright new-shoot greens, but it seems that Cobalt Turquoise will also get you there!

Let’s take a closer look at these, and other color mixes.

Color Mixes

Note I’ve used various brands of PG7 over the years, but they are pretty much indistinguishable.

Hansa Yellow Light (PY3)

Exploring various aspects of the Hansa Yellow Light (PY3) mix previewed above, it’s clearer to me that the Phthalo Green mixes have a tighter hue range (green to yellow-green) while the Cobalt Turquoise mixes can move more into a seafoam area. However, the Phthalo Green mixes can go darker. Cobalt Turquoise mixes are always kind of light-valued.

Imidazolone Yellow (PY154)

Same conclusions as the PY3 mixes above, though overall both sets of mixes are a bit warmer and do not get as bright.

Nickel Azo Yellow (PY150)

There is something wonderful about Nickel Azo Yellow (PY150) in its capacity to make deep greens that are bold but somehow still look naturalistic. They just have this intense juicy look. This is true of both mixes here. The Cobalt Turquoise mixes are, as ever, cooler and more textured.

One thing I find interesting is that a mix of Cobalt Turquoise + NAY that is mostly CT looks a lot like mid-tone unmixed Phthalo Green to me! It does not get as dark of course, because CT never does.

Green Gold (PY129)

Green Gold (PY129) takes the place of a traditional yellow to make these blue-toned greens more yellowy, juicy. Like Nickel Azo Yellow, they have the metallic-paint superpower where they can be quite bright but also naturalistic. Both of these mixes are great. I think the Phthalo Green mixes look more like a traditional “on the nose” middle green (kind of like Hooker’s Green), while the Cobalt Turquoise mixes have an oddness to them that I find fascinating. The texture makes them great for foliage.

Quinacridone Rose/Red (PV19)

While I wanted to focus mostly on yellow, let’s take a quick look at some other color family mixes from the archive.

Phthalo Green is almost a complement of PV19 rose, so they make gray together, while Cobalt Turquoise being more blue makes a violet. The floating granulation also makes the Cobalt Turquoise violet mix look light and ethereal, while transparent Phthalo Green mixes more completely and in a more workmanlike way.

Dioxazine Violet (PV23)

A cool thing you can do with violet and green or turquoise is to make shades of deep blue. With Phthalo Green, you can make very deep, muted blues; the blues with Cobalt Turquoise are much cleaner and lighter in value, and stick around the mid- or violet-blue range. You can make a surprisingly good Cerulean clone.

Getting from One to the Other

Mixing Turquoise Hue from Phthalo Green + Phthalo Blue

Adding Phthalo Blue Green Shade is the best way to get a Cobalt Turquoise-like color from PG7. (Phthalo Blue Red Shade also works, but not as well; it’s a bit too muted.) The mix of Phthalo Blue and Phthalo Green makes a range of turquoises, with the more diluted ones having a bright turquoise hue that is very similar to Cobalt Turquoise. Keep in mind that the other properties will still be totally different.

Conclusion

Despite their obvious differences, these colors may serve surprisingly similar roles on the palette when it comes to mixing greens. Either of these would make great additions to a bold spring palette palette. I’ve historically had both – but I think I may only need one.

These differences in properties can help to choose between them:

PropertyPhthalo Green (PG7)Cobalt Turquoise (PG50)
Base hueEmerald green (add Phthalo Blue to make turquoise)Light turquoise (add yellow to make emerald green)
TransparencyTransparentOpaque
GranulationSmoothGranulating
StainingStainingLifting
Value RangeHigh value right, light to darkLight to middle values
ToxicityNontoxicToxic
PriceInexpensive (series I)Expensive (series III)