4th one, Dragon's Heart. I just finished it last night.. and finally found out what color Sssargon is, but the base colors of his sisters remain a mystery.
I agree that for the most part her descriptions are wonderful, but there are just a few points, like with the 5 dragons who feature so prominently in the 3rd and 4th books, but have hardly any physical description, compared to once-offs like Mighty Mo who got lavishly described during the fight with poor S'Blood. I have similar problems with White Jenna and Sister Light, Sister Dark. Most of each book is very sound, but then a few scenes(not even consecutive ones) lack in detail, like there was another author or a heavy-handed editor.