IDK. I haven't heard that either. Foaming is usually from splashing/agitating or spraying (under pressure) of fluid, not a contact issue. Anti-foaming agents are added to hydraulic fluid. Like skid steers or heavy equipment, they often have an anti-foam agent to add to motor oil (the hydraulic fluid in equipment). Still, I do use ..or have used the gray. It doesn't *seem* to exhibit properties different than other sealers (Ultra's that is), at least by eye. One advantage of the gray is its slightly easier to see leaks, which don't happen very often if you do it right. I've used red but not for many yrs.
A long time ago, like in the 80's/90's, most silicone sealers ya bought, esp the black, weren't all that great. They were almost terrible, like cheap bathtub sealer. And AFAIR, the gray and the red was akin to the Permatex Ultra. I remember the red being the high-temp stuff. Then Permatex Ultra line sort of caught on and now ...who buys the el-cheapo stuff anymore?? So maybe that's where it came from: 'If you used the gray or red product it was essentially by default the 'good' sealer, whereas back in the day, the black could have been the el-cheapo original silicone sealer ...which didn't work all that great and might or might not leak. But that's just conjecture on my part. I've used plenty of black Ultra on tranny pans and diff covers (and other items) and never had a problem.
It's probably just Chrysler stocking two part numbers for reasons that nobody can remember. They've recommended gray for 20+ years.
