I don’t want the blue strip that is the header (or any other color). I just want to place my logo there.
Open the STYLE tab of your survey and click on the HEADER option. You can change the header color to anything you want.
See the SurveyGizmo documentation for details – https://help.surveygizmo.com/help/add-header-image#add-colors-and-a-logo-to-your-survey-header