2- Yes, blue is through, means the colour is not on-trend any more.
3- Puce isn't used terribly often. However, if you work a lot with colours you may use it as you need to describe very specific colours. Puce is a very rich, saturated shade of purple. Quite like a plum. I hear the word puce mostly if one is describing someone's face. For example, if someone goes really red due to being embarrassed- 'they turned puce!'
5- Yes, rust is a deep shade of orange. If you want to know exactly what it looks like you can Google 'core ten steel'.
6- A bust can either he a head (like a sculpture of a head that you have for decoration) or breasts. In this case I think it means that it is fashionable to have smaller breasts and 'the look' (the clothes) are designed for people without big breasts.
9- I have never heard this expression. To be honest, I would not use it, just to be 'politically correct'.