Title says everything, so I’ll just leave you with a screenshot. I will answer questions if needed.
You can change the transparency in the menu with the color wheel.
also, naturally the opaque-ness of glass stacks, so if you have 2 panes of glass overlapping it will be more opaque, this will be more noticeable if you are making a larger structure and need to panes next to each other and the edges overlap. also if i remember correctly 0% transparency makes glass invisible
Ah, so the problem is that glass walls became colorable and they default to having no transparency. Got it.