Ok so I'm seeing loads of videos popping up claiming that Meltan and Melmetal are hinting at Armoured evolution in Gen 8 because they change colour when they touch a crystal in Let's go.

Time to put this to bed by looking at it logically.

Meltan and Melmetal have a red tail (blue when shiny) let's go is based on yellow.

The original 2 game boy games that we got were Red and Blue.

Meltan and Melmetal are Silver but turn Gold when touching a Crystal.

Gold, Silver and Crystal being the Gen 2 games.

If anything this is a very subtle nod to Gen 2.

Bringing it all together, Meltan and Melmetal are one huge nod towards the whole original GameBoy games.