You're referring to "Slime"?

That brand and trademark has been around for years. Best-known
(first?) product is a fiber-loaded gel that you can squirt in a
tire, before inflation... in the case of a small puncture, the slime
flows into and blocks the puncture and keeps the tire from going
flat. Or, so they claim.
It's bright green, and slimy. Truth in advertising :-)

Thanks for the correction. I'm glad to know there's a good reason for the
name.