Unfortunately most the answers you are getting are from pure Trigger and Script coders, so your answer seems to have no clear answer.
It is impossible to change a hero or unit's team color to white, as hero glow and team colors are done like so by a modeler:
The area where you want team color to show up is alpha'ed out on the model. The team color is then added in via some edits to the model, which can be done via notepad.
Only the 13 team colors are available as team hero colors. If you want to create a white "team color" you will need to open the model, fix the alpha channel, and color the alpha'ed out area to white.
You will then need to replace the specified unit you want with a duplicate, similar unit that has the same model.
It's really quiet a lot of work and even more difficult for an entire team's units to be changed, and totally not work it. But if you want to try it, ask the model section for more info.