I can't find anywhere what the color of disodium phthalocyanine is. Do you know?

That's an interesting question. The phthalocyanine dyes we work with generally contain a copper atom at the center of the phthalocyanine ring, so I always assumed the copper was necessary to the color. Copper sulfate is a similar lovely turquoise color, after all. Disodium phthalocyanine lacks the copper, so what color does it turn out to be? 

An MSDS at Fisher Scientific says the undissolved, undiluted powder is blue-black, while, in contrast, an MSDS at Strem Chemicals describes it as a purple powder. The color of the dye powder doesn't tell you the color in solution, though. We often notice that the undiluted dye powder is often a bit different from that of the same dye in solution, usually much darker.

On the other hand, without the sulfonate groups typically added to a dye's structure to make it soluble in water, disodium phthalocyanine is apt to be extremely difficult to dissolve in water, anyway. How do you use it?

Sigma Aldritch says the absorption spectrum of disodium phthalocyanine has two peaks, the larger one at 649 nm and the smaller at 721 nm. Comparing that to the absorption spectra on this page for a reactive dye that contains copper phthalocyanine, it looks clear that it must be turquoise in color. They describe their disodium phthalocyanine product as having a dye content of 90%.

Wikipedia says that even metal-free phthalocyanine is blue in color, but of course you always need to get independent confirmation of anything you find there. The article looks credible, though. 

There are some fascinating old videos available online about the discovery of the phthalocyanines by Sir Patrick Linstead. Look at these:

• Introduction: Patrick Linstead: Phthalocyanines [.mov]
• Index: Patrick Linstead: Phthalocyanines [.mov]

They load slowly but are worth the wait. It's astonishing now to see the chemist doing experiments, some with nearly explosive results, without any safety glasses or gloves, and smoking a pipe or cigarette throughout.

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