Is there a reason other than aesthetics that glass needs to be sorted? Do the chemical colorants not work well together, or is the glass types incompatible with

Is there a reason other than aesthetics that glass needs to be sorted? Do the chemical colorants not work well together, or is the glass types incompatible with each other? Wouldn't multi-colored glass that looks obviously recycled be a product that would be attractive to "green-conscious" companies?