Yep, you did here is the MEMO 
FYI
Not a direct answer for you, but @Satur9 posted [this] in the xLED thread and it has some info for you,EDIT But nothing at all to do with SIID or LEDs
For what its worth, I would have assumed brightness on either
ROYGBIV or Colour LED voltage which is similar.
Guess there is a dash of electrical alchemy and a pinch of magic smoke and mirrors at work
