Adding a little bit of iron to glass does makes it green (don't know about fuzed silica or quartz). Supposably manganese acts as a clearing agent for glass and can counter act the effect of iron.

Is there an iron-free silica source on Mars?

Don't have a clue. We need to find out.

Is there manganese deposits on Mars?

Don't have a clue. We need to find out.

Of course before we can allocate Mars exploration resources towards finding critical ore bodies, we'll first have to focus our full attention towards searching for the nonexistant liquid water along with the nonexistant Mars fungi.

It's important to have our priorities straight!

Gary