Thanks for letting us know about the situation. We'd love to help you with this.
The color that seems to be in your header background image might be of Fallback value Please make sure that you have selected header background color and fallback value as transparent. Follow the steps to set the background as transparent
Open TemplateToaster->Your Template->Header->Background->Transparent color-> Images->More images->Fallback Value-> Transparent
We hope this is helpful. Let us know if you have any more questions, comments, or concerns.