I'm a little confused. You state you're testing a Silverlight application then talk about how Test Studio is not highlighting a HtmlInputText. This confuses me because Silverlight applications don't have a HtmlInputText control. They only apply to regular HTML applications, not Silverlight applications.
For highlighting, have you looking into our own Annotation feature (step 5 of this page
)? Test Studio can do all the highlighting plus annotation for you. However it won't "highlight the normal fields with "red" color and for verification/validation purpose I need to use "green" color". Test Studio will use the same color throughout the life of the test.
You could also try our custom annotator from code
That's all I can offer for now. To do anything more for you I'll need a copy of your test plus access to your application (a URL I can connect to) so I can run it and see the problem happening on my machine. Then I can diagnose why it's not working as expected.