When the Bourbon king Ferdinand IV reconquered the city, Colletta was thrown into prison and only escaped the death penalty by means of judiciously administered bribes.

When the Bourbons were expelled a second time in 1806 and Joseph Bonaparte seized the throne of Naples, he was reinstated in his rank and served in the expedition against the brigands and rebels of Calabria.

At the outbreak of the revolution of 1820 the king called him to his councils, and, when the constitution had been granted, Colletta was sent to put down the separatist rising in Sicily, which he did with great severity.

In 1823, he was permitted to settle in Florence, where he spent the rest of his days engaged on his Storia del reame di Napoli.

[2] His Storia del reame di Napoli dal 1734 sino al 1825 (first published in 1834), which deals with the reigns of Charles III and Ferdinand IV (1734–1825), is still the standard work for that period, but its value is somewhat diminished by the authors bitterness against his opponents and the fact that he does not provide references for his statements, many of which are based on his recollection of documents seen, but not available at the time of writing.