Slingerland called it "Beige weak chocolate milk."

Yes and from what I've read it's more of a stain than a paint. I'm sure the batches had some color difference as it was just a interior coating. My 68 shells have almost a pinkish hue to them inside. A few guys have matched it I think. There's been a few threads on DFO about it a while back, year or so. VDF member Bill H used a Krylon color to replicate the color. My bass drum was painted black inside so it was a total cover up job for me and matched pretty well.