Neutral Color Superconductivity and Pseudo-Goldstone Modes
  Four of the five expected Goldstone modes, which will be eaten up by gauge fields, in neutral two-flavor color superconductor are actually pseudo-Goldstone modes, and their degenerated mass is exactly the magnitude of the color chemical potential, which is introduced to guarantee the color neutrality at moderate baryon density. 
Lianyi He, Meng Jin and Pengfei Zhuang