First, SwingX suggests not using TableCellRenderers that are a subclass of DefaultTableCellRenderer. It is a poor implementation of a renderer and it also does not take advantage of the SwingX rendering paradigm of StringValues (for display text) and Highlighters for visual decoration. I'd recommend replacing your custom DTCR subclass with a DefaultTableRenderer that Highlighters, such as HighlighterFactory.createAlternateStriping().
Second, if you continue using the DTCR subclass and it handles colors correctly (because DTCR does not), you may need to call JXTable.putClientProperty(JXTable.USE_DTCR_COLORMEMORY_HACK, null). This should causes JXTable to honor your colors.