The system themes are described on MSDN, where you can also download the default Styles and ControlTemplates applied to the native WPF controls Syncfusion MaterialDark theme for WPF. This example shows one way to use the TextChanged event to execute a method whenever the text in a TextBox control has changed. In the code-behind class for the XAML that contains the TextBox control that you want to monitor for changes, insert a method to call whenever the TextChanged event fires. This method must have a signature that matches. In WPF to have text with different colours you need to use a RichTextBox. There is one colour available for a TextBox. gt;>Example the Text is "Hello" with foreground color as Black, now if I type "World" in the same textbox I need to change the foreground color. You can try the following sample (use a ValueConverter).