When transplanting anything, remember it will go into transplant shock. Won't want anything much to eat and drink for a couple of weeks. Will look and feel as droopy as you would after a transplant operation!

Stop trying to drown the poor thing.

And most purple basils will revert to green. Opal basil does it faster than most.

Three basils in one pot! That's like 3 generations of humans in one small room. Too much competition, too little space, and before long some 'must go'.

Take the risk of moving your purple basil again, this time to its own private home - and this time don't water it for a day or two. Instead, gently tamp the soil around the stem. Water it only when the soil is no longer moist at finger-tip depth.

There's nothing you can do to stop it reverting to green.

I have to ask, will it have the same taste? if its not purple?

It'll taste just like sweet basil, which which is has been derived.