I have many hundreds of the Gallia 15mm Warring States Chinese range but none of the Colonials.
For what it is worth the Chinese are a perfect height and bulk match with Chariot and Outpost 15mm, slightly frailer than Minifig but same height. I mix figures from the 4 ranges without any issues
I think they would work with Donnington and early Gladiator also.
Comparing to other era 15mms in my collection they are a head taller than Peter Pig, Naismith or Essex but similar bulk, YMMV but I don't think they look right together
Similarly with bigger/bulkier ranges like later Gladiator, Lancashire, Old Glory or Museum these all make Gallia figures look small and puny.