Is there a shiny Missingno.?

Sorry, there's no shiny version of MissingNo.

MissingNo. only appears in the non-Japan Generation I (Red, Blue, Yellow) Pokémon games. Said games, being designed for the monochrome Game Boy, do not have shiny Pokémon. Therefore, MissingNo. cannot be shiny in Generation I.*

You also cannot trade MissingNo. to Generation II (Gold, Silver, Crystal) games. Since MissingNo. can't exist in those games, it can't be shiny in Generation II.

However, there are other glitch Pokémon in Generation II and beyond, and after a quick look at some of those pages it seems reasonable several of them could be shiny.

* Assuming the definition of "shiny" is "the game calls this a shiny Pokémon, and displays it in a different palette". Because Generation II uses hidden values of each Pokémon to determine whether it's shiny or not, and these values are in the Generation I as well, you could argue the first generation does have shiny Pokémon -- it's just that they don't have any outward difference until they're traded to Generation II.