Adjust>Color>Channel Mixer
Output channel: grey; red: 94%; Green: 101%; Blue: -6%; Constant: 15%; Check Monochrome.
You can see how OCD I am! I played with that greyed pattern with everything I could find: Adjust>Color; Adjust>Hue, Saturation, Lightness>colorize and everything else. And I even played with AI resize to increase the 600 px size to 700, then to 800, then to 900, and then to 1000. This was because I couldn't get a good pattern to cover a 3600 px page. If it takes it, I will post it as 1000.