Three-quark colour singlet ($|1_c⟩={ϵ}_{abc}|abc⟩/\sqrt{6}$)

The invariant colour state of three fundamental quarks is the normalized completely antisymmetric tensor ${ϵ}_{abc}/\sqrt{6}$. With this colour factor, the Pauli exclusion principle requires the remaining spatial-spin-flavour wavefunction to be symmetric. Colour and approximate flavour symmetry are distinct SU(3) actions.