Change color of part of a text field UI toolkit

I am trying to make a text field, using the UI Toolkit, that when the user type “Hello world!” it changes the color of “Hello world!” to green, but if I type “Hello world! Who are you?” it would only make the “Hello world!” green, and the rest would be the default color.

I hope I gave enough info. if I did not then please let me know. Thank you a lot for looking at this.