Why a consistent colour coding is important - recycle bins

Looking at more recycle bins, some at the airport, some at a company building, I realised there's no common colour code to refer to different items.

So, for instance, people coming from Italy to London Heathrow and back would probably misplace some garbage because of the different colour code vs expectations.

Milan Linate vs London Heathrow
general waste: blue vs white
paper: white vs blue
platic: yellow vs red

But there's more: within the same city I found another colour code inside the one Company I visited.

Shouldn't we try to define a common colour code? 

I know there might be issues depending on the country (have a look at this infodesign to see what I mean), but I think that even a common colour code within a country would improve recycling habits a lot by leading to less misplaced garbage.

And recycle bins would be useful, then. :)