Chet Shink, PhD, managed the Electrochemistry Engineering group and was looking for a way to improve in-plant chemical safety. He came up with the four color diamond-shaped tag which was adopted by the industry. The blue square represents the health hazard, or toxicity, red represents flammability, and yellow represents reactivity. The numbers are 0 (low) to 4 (high).
This August 1970 Tekscope details the hazardous material identification system. Click on the image to view the PDF.
More information on Chet is on the Chester Schink employee page.