Weeks ago Apple's CEO tweeted: "Seiko Advance is a great example of our invaluable suppliers here in Japan. Thanks to their craftsmanship and attention to detail, the gorgeous colors of iPhone 11 Pro really come to life!" Our cover graphic shows Cook at the Seiko Advance plant in Japan that makes the iPhone 11 Pro's killer Midnight Green ink.

In a new Nikkei report today we learn that the Seiko Advance plant is the only ink plant in the world that has a cleanroom allowing the control of temperature and humidity that controls quality.  

Apple probably chose Seiko Advance for creating their inks without using pollutants like halogens that is usually required for creating the Midnight Green color. 

Nikkei's report notes that the sales manager of Seiko advanced promoted that fact that they've developed a cleaner way to make their inks, including all of the other colors for the iPhone 11 including the Space Gray, Silver and Gold.

Seiko Advance didn't originally win Apple as a customer when they first visited Cupertino to make their sales pitch. The quality of their ink originally didn't meet Apple's high standards.

Through trial and error Seiko Advance was eventually able to inch into the iDevice market with Black ink for the iPhone and now Apple is responsible for 40% of their sales.  

According to Cook, Apple and Seiko Advance have "grown together" and "push each other to innovate more." For more on this, read the Nikkei Asian Review report titled " Apple ink supplier in Japan makes mark with iPhone 11 Pro colors."