DSCN2825 by daddeee, on Flickr
DSCF1206 by daddeee, on Flickrsorry to derail OP's thread, I had DIY RB CW leds and ran them for a year before adding T5 back. Don't have any pics, but the reason for adding the T5 was the mille. PE was good but growth was not, millepora would encrust like crazy but not grow new branches. I am sure the LED fixtures on the market today are better than what I was running at the time.
Rovster, I can believe that coral has all those colors, especially if it the same piece. Nicest Mille I have ever been in possession of. I lost the colony in the AEFW battle, RTN'd overnight. I sold and gave away many frags of it to spread around around and no one seems to have it..grrrr!!
DSCF1206 by daddeee, on Flickr

I think it can have something to do with what kind of LEDs you are using actually. Millepora is a shallow water Acropora and is exposed to a broad spectra of wavelengths. With narrow band spectra LED's it might not flourish.
This is not fact, just speculation from me, after some disussions with LED users frustrated over the sudden problems with Millepora, an Acropora they earlier have had good success with and that is generally considered to be one of the easier Acroporas out there.
That could be a problem for any SPS, not just millepora. RGB LED units should not be used for a reef tank, nor should a LED unit that lacks a broad spectrum white of some sort. The white will fill in the gaps, so to speak, between the narrow bands of color from the non-white diodes.
12-27-2011-3 by daddeee, on Flickr
DSCN2377 by daddeee, on Flickr
DSCN2308 by daddeee, on Flickr