Diagnosis
Flash rust. It happens when moisture hits the bare steel before or during the oil application, or if the initial oil layer was too thin. The steel is incredibly reactive.
How to Fix It
Right after cleaning and drying, you have to move fast. Get the griddle surface hot (about 200-250°F) to drive off any residual moisture, then let it cool just enough that oil won't instantly smoke. Apply a very thin layer of your seasoning oil (canola, flaxseed, etc.) with a paper towel—so thin it looks like you almost wiped it all off. Then crank the heat to high to polymerize it. That first micro-layer is a moisture barrier. Repeat 2-3 times.
If That Didn't Work
You might be using a water-based cleaner or leaving it wet. After washing, dry thoroughly with towels, then immediately do a quick heat-and-oil cycle. Also, avoid storing it outside with a cover that traps humidity; moisture will condense under the cover.
Heads Up
Don't panic over a few tiny orange spots. Just scrub them off with your scraper while the griddle is dry, re-apply a thin layer of oil, and heat it up. Seasoning is a maintenance layer, not a permanent finish. It'll build up over time.