What do you think shininess to do with Pokémon evolution, if anything? I remember in the Johto games, the shiny Gyarados was red because it was force-evolved from the naturally-red Magikarp, right? And is it a coincidence that Mega Charizard X has similar coloration to a shiny Charizard?
I’m sceptical. Like, what happens at Lake of Rage, supposedly, is that they’re forcing a whole bunch of Magikarp to evolve. The red Gyarados that you fight isn’t the only Gyarados there, it just happens to have caught everyone’s attention because… well, it’s red. Team Rocket’s original plan in Mahogany Town (aside from perfecting their radio technology for their later plot in Goldenrod City) was to turn a tidy profit converting useless Magikarp into valuable Gyarados – not just one, but several. Honestly they probably would have been better off without the extra attention drawn by the red one, but once people did start getting curious, they opportunistically started making a bit of extra money on top of that by setting up a toll booth near the lake. Or at least, that was my reading of it.
I don’t think it’s a coincidence that Mega Charizard X and shiny Charizard are both black, but I don’t think that’s the direction of the causal relationship; I think they’re both black because of a third, unrelated factor – namely, black Charizard are super badass (also, none of the other mega evolutions have this relationship, and the only one who does, Charizard, also has another mega form that doesn’t).