moonpod,
How long is it ? The fin coloration seems transparent, but as you say, if it is over 7-8cm long it can flash. The reason for non-display seems that there is no other "males" of Paracheilinus or environment of your tank. I always turn off all the light in the room but that of the tank, and you may see it flash in the evening to night.
scchase,
Yes, yours is very similar but the dorsal-fin color is differing a bit. It also has a purplish body like P. cyaneus. Anyway keep me informed and get more pics to show here, please.
snorvich,
Thank you for your future pics, and I will greatly look forward to seeing them.