After 186K mile, I've decided it's time to rebuild the bottom end of my L24. Figured since the engine would be out, it would be a good time to paint the block. Researching this forum, I saw a reference to Glidden code GL31557 as the Nissan OEM color. I decided to contact Glidden to see if they would have formula for that color. When I contacted them, it appears the automotive paint products were sold to PPG. I contacted the PPG color library. They could not match the code but found two engine codes for Datsun, a Blue-Gray # 19885 and a light green #48104. Unfortunately, these codes only came in an expensive, single stage Acrylic Urethane paint and would require an Epoxy Primer. While this combination would be a hassle, it would be worth it to get a fresh, non-faded color sample for others to color match. They did not have any color chips or online resources to confirm the color and referred me a local distributor. So this afternoon, I took a 30 mile trip to the nearest distributor and had him mix up a pint. I was expecting a darker teal blue from my memory of my '68 510, but when they brought up the can with a sample dot, it was definitely a medium gray with just a tinge of blue. They double checked the formula it was correct - just not anywhere near the color needed. So just another blind alley. Hope this posting helps others avoid the waste of time.