Just one reply at the moment and not really good.
( google traduction)in response to your question, this seems unlikely because the command vehicle , depending on its level, is intended rather to the number of radio antennas. Stencilled were affixed upon the arrival of CEFEO because it was used in the DB. The more necessary discretion require too precise ban all forms of identification in order not make targets for the enemy ... even among the riders!
But ,like you I've found some photos with pennants on véhicules ( most are weasel or LVT4)
I spent a couple of hours looking for information but I don't find anything.
The only text that I 've found talk about a red pennant for "chef de section"
Despite I found information for the beginning of WWII ( 1940) but I 'm not sure it was still used in Indochina.
1940:( google traduction)
The command pennant consists of a triangular flame 40 cm long fixed on against a metal pole over a length of 30 cm. The iron pole was 1 meter 20 long and 8 mm in diameter, so they can spend easily through the slot. it ends with a wooden handle for easy handling ... "
" The flame of the flag is variable in color . This is characteristic of the tank commander 's rank. The white and green colors are those of the company commander, white and red colors throughout are those of the section head , color red is one of the leader half-section, the blue color is that of the gunner tank commander . "
" Each tank also has a second flag square yellow flame of 30/30 , which is used to indicate that the tank is down. This flag remains visible as the car is locked . "
1940 pennants ( from Liliane and Fred Funken books)
6 chef de section
7 sous-officier adjoint
8 char subordonné
9 commandant de compagnie
10 fanion de panne.
Still looking for informations.