Duskling: if you have time to look on the old forums, there is a huge thread dedicated to the discussion of Shadowling colour and aging, and, effectively, it's all been worked out. There is a connection between colour and age for Shadowlings, but it's relatievly loose one, that is to say- it's more like how would a person appear to someone else, rather than real age- some age quicker, others more slowly, so Gen. Darkeye is still "in good chape" for his age. The way it goes is the following: red are youngesters and into adulthood they remain red, purple is circa 40ish in human terms, then blue comes over, then, towards the end, they go green. Shadowlings of exceptional power,such as Nelis or Tastidian, are not quite on the same level- they simply glow, with that Psy power emenating from them.
Whilst on subject of Shadowling peculairities- horns are just a curiosity, a something that some Shadowlings have whilst others don't- there is no correlation between age, military rank and number or even presence of horns.
It's nice that you've brought this old subject up though
