Didn't see this thread before..............but I need to make it clear, that pic.s and description of colouring up is defenitely referring to another species, namely Rotala rotundifolia!!
Rotala sp. 'green' will not colour up, even in brightest light, but remain a bright green - hence the name.......
Growth-patern of Rotala sp. 'green' is actually not the same as of Rotala rotundifolia either. Rotala sp. 'green' has a much more "overhanging" or "fountain"like growth, whereas Rotala rotundifolia has far more "straight" and "up-going" growth.
- for trimming of both kinds, I'd actually recommend the "Black Current Method" - which means cutting back (quite low) a third of any given group of stems - wait a period of time (different for different set-ups) and cut another third of stems - wait again, and finally cut the last third of stems..........and then wait, and start all over again.
The idea is, to allways cut away longest (oldest) stems in a continuous cycle