SU(5) iself can be decomposed as SU(3) times SU(2), amounting to two kinds of flavors. Five preons if you wish. They have electric charges -1/3 and +2/3 respectively,
[tex]
5 = 3 +2 = (-1/3, -1/3, -1/3) + (2/3, 2/3)
[/tex]
[tex]
5 = 3 +2 = (-1/3, -1/3, -1/3) + (2/3, 2/3)
[/tex]
[tex]\begin{pmatrix}
\nu & \nu & \nu & e & e \\
\nu & \nu & \nu & e & e \\
\nu & \nu & & e & e \\
\bar e & \bar e & \bar e & \nu & \nu \\
\bar e & \bar e & \bar e & \nu & \nu \\
\end{pmatrix}
[/tex]