I wonder if there is such a thing as transparent grey. The question has come up while designing a window which the client would like in neutral tones, like my inky black and white drawings. All the samples I have made so far have too much colour in them, this comes from the metallic elements these powdered enamels are made of. So I thought of watering down an opaque black with a transparent flux, which was the point at which I realised there is no such thing as transparent black, nor therefore transparent grey. All the areas that look grey aren't very transparent, they're full of small black bits suspended in a clear medium. And there is no such thing as transparent white either, which could be why we stained glass people call clear antique glass "white".
Colour compositions in stained glass using pieces of transparent coloured glass, like the one above (made by my daughter/work experience student), benefit from a lot of neutrals amongst the bright colours. Sorting through my scrap box I found a selection of neutrals and some opaque black and white - that's as close as it gets to grey. The pieces I was looking at on my lightbox (above right) led me to the words of my favourite Thomas Hardy poem, I can even see the pond and the winter leaves in the glass. It's like that outdoors today.