I don't think that is correct - you cannot (easily) do anything on the local machine that will change the prompt generated by the remote machine.
You must make the change in each ~/.bashrc on the remote machines.
I use something like this on all of my own:
#Make prompt colored when logged in remote
export NON_LOCAL_LOGIN=`env | grep SSH`
if [ "$NON_LOCAL_LOGIN" != "" ]; then
Just add that to the ~/.bashrc on each remote machine and you will be all set.
You don't need it until you login so no need to change them all at once - just keep the code snippet handy and when you login to a non-colored prompt add it to the .bashrc.