The information I posted in the xLED thread related to the xGLO implant, and the luminous intensity of certain phospors when they’re bombarded with beta radiation. LEDs through the skin have slightly different mechanics.
The Green LEDs have the greatest light output, but that doesn’t necessarily mean they’ll appear the brightest. There’s other factors to consider, like the absorption of certain wavelengths of light by your tissue, and the perception of brightness in the human eye. We’ll all have to engage in some more testing, but I would wager that the red xSIID will subjectively appear as bright as the Green.
If I were you, I wouldn’t be so concerned with “brightness”. Pick the color you like. They’re all cool.