I've recently been looking for some nice shading purples and green inks. I would like them to shade in a fine nib, but if the colour is gorgeous enough, I would definitely consider getting an ink that would shade in say a medium or broad nib or a flex pen. I think that this would be the best place to go for some recommendations. Some requirements:
1. It must be well behaved. Excessive feathering is a no.
2. It must not stain white pens and should be easy to clean out.
3. If purple, I'm looking for something around the range of Waterman Purple or Scabiosa, nothing too blue.
4. If green, I'm not very picky but I would rather not go for R&K Alt Goldgrun. That colour doesn't appeal to me.
5. I may change my mind on the above if I can get some colour accurate pictures (not scans). I've only seen scans and ink swabs of the aforementioned inks.
If I think of anything else, I'll edit it onto the original post and put it as a comment. When edited on to the original post, it will be marked with an asterisk.