Almost as good as the elusive Tup wool.
I imaging colour to be slightly pinkish/effeminate and slight limpness to the wrist area. Could also contain shades of blue/grey/black of frustration!
Most Old World dressings that call for Capon are red in colour and often used for body palmer patterns.
Capon feathers are roughly the same size as Cock feathers but softer/fuller and webbier than true Cock hackle- especially genetic hackle of todays dry fly mentality.
We would often refer to such hackles as "Henny/Cock". I find a lot of similar style feathers in Indian and Chinese Cock capes that can be had cheaply over here.