Technically, the CYAN will be brighter
1) It is not doing a secondary conversion (ie Blue->Phosphor White)
2) The longer wavelength LEDs are more eff
3) Your human eye is more sensitive to CYAN
But, I would caution againest just buying the "brightest" color, for millions of years - us humans are used to having a light source from the Sun which is "White", any other color - although "Brighter" will seriously corrupt our perception of colors, or in simpler terms
If you look at things with a non-white light; all the colors will be "messed-up"