Oh that looks so awesome , a dragon in actual stained glass form, sure like to see something like that more often. Now I am not sure if you would know if the glass was blown and while hot made flat, and let to cool and colored the old fashioned way or don in a modern technique or not. For sure do think that either way, your design, his glass craftsmanship the finished product looks great.
So it was done in the old fashioned style then, at least somewhat. I would guess then that the yellow was most likely made from chromium, all the useless thing you find from watching Hunting the Elements, and reading ore into the subject.
Okay, then I am envious of YOU! Really, it's brilliant work. Stained glass is one of those artisan crafts that I've not yet tried, and it looks like a lot of fun (and marvelously tedious, detailed work).