Whilst obviously not a French territory (although the French did hold various treaty ports in the country), it is little-known that France sent troops to officer, drill and train Chinese irregulars in response to the Taiping and Nian Rebellions which began in the 1850s. The French-officered army was coined the 'Unvanquished Army' and consisted of several thousand volunteers, whilst its equivalent Anglo-American-officered army was known as the 'Ever Victorious Army'. These names were derived from monikers assigned to the armies by Qing China for recruitment purposes.

Both armies were the first truly modernised forces that Qing China would field, and whilst producing mixed results on the field of battle undeniably contributed to the curbing of the devastating Taiping rebellion - being present during the reclamation of both Zheijiang and Jiangsu. Both armies only existed for a few years before disbandment due to widespread desertion.

This doesn't strictly answer your question as to French territories but I think it's fascinating to read about regardless.

Source:

China: A History - John Keay