I've just noticed the sun shining through some of my clear glass rods and realised there is a huge difference in colour between the three different manufacturers. These really are clear when you pull them out and look at them but the chemical mix in each 'clear' gives them a tint when light is shines on the end of the rods. These chemicals react with the chemicals in the glass you mix/cover them with to get different colours/reactions.
It's no wonder lampworking is considered a 'dark art' by many - what you see is so often not what you get! :D