How can we show the applicant they've successfully submitted the form

People filling out the form on our website don't know whether they've submitted the form successfully or not.  Applicants often will submit the form multiple times.  Is there a way we can fix this?  

Thank you for contacting us.

I have changed the submission message font color from white to black on your form Thank You page.

The text seems to be appear normally now. 

I you need any further assistance, please let us know.