Quark doublet ($Q_L=(u_L,d_L{)}^T\sim (3,2{)}_{1/6}$)

In one Standard Model generation, the left-handed up and down quark fields form a weak $SU(2)$ doublet of hypercharge $1/6$. Each weak component has three colours. The same field therefore counts as three doublets for weak gauge-loop contributions and two colour fundamentals for strong gauge-loop contributions. Right-handed up and down quarks are separate weak singlets.