Lead design. How thick are these? And what colour does these come in?

Lead work comes in various sizes from 3 mm thick to 9mm usually it’s a dull lead on the external unless fit between the 2 pains of glass that then keeps it looking shiny and more new looking

Lead comes in three sizes 6mm, 9mm, 12mm 9mm is the most common All lead is silver in colour when new but will oxidize to a dark grey or even black look but bear in mind that the lead strips are applied to both sides of the outer pane and as the inside of this pane is inside the sealed unit, will not oxidize and will remain silver. hope this helps