Fortunately (I hope), I bought and used cans of original GM splatter paint years ago, for my restoration. I must assume that it was GM over-the-counter service paint. It looks very close to what I have observed in original/survivor cars. However; I would agree with Jerry@CHP because of the batch lot and spray patterns with a pro spray guns may not match that from a repro rattle can.
If you do buy repro rattle cans (like most of us need to do), test it on card board and look at it for a day to two, to comparer it to the "original" splatter spray in your trunk. Buy 3 – 4 cans and a couple cans of sealer made for splatter paint. You may need touch-up paint at some point in the future. If only the absolute correct spray is desired, Jerry provided several good sources. I have purchased numerous parts from Larry C. He has a very impressive lot of Camaros, and is a good resource for info.
Note in the pics that the camera flash can washout the color so that the black/aqua may look black/gray to black/white. So verify with documentation or pics of your own trunk paint if original to try and duplicate it.