read the docs in JList on using a ListCellRenderer.  Are you sure you
mean JList not JTable?

If you meant JTable, you want to write a TableCellRenderer.

You might want to read the chapter in a Swing book on these beasts.

The crucial fact to keep in mind is that the default JLabel component
you render is the same for all cells, so any changes you make to it
will reflected in all other cells. In other words, set ALL the
attributes you change for any cell.