the Text Editor you are using is a template. The desired special behavior (e.g. border color) is custom specific and has to be added to this template explicitly. How you do this is up to you. Possibly approach:
1. Add a Border view to the Text Editor component.
2. Arrange the Border view to fill the component's area.
3. Configure the Border's property Layout to the value Core::Layout[AlignToBottom, AlignToLeft, AlignToRight, AlignToTop, ResizeHorz, ResizeVert] This ensures that the position/size of the Border view is automatically adapted if the Text Editor component is resized at the runtime. See also the section: Configuring component layout.
4. Within the Text Editor component open its method UpdateViewState() for editing. This method is executed each time the state of the component changes. For more details see the section Common component states.
5. In the method UpdateViewState() add following code to show/hide the Border view depending on the Focused state of the Text Editor:
Border.Visible = aState.contains( Core::ViewState[ Focused ]);