In your theme folder > styles > sass > lib > components there is a file called "dataview.scss" where the styling for dataviews is maintained.
Looks like the styling for the control bar is held in a class called ".mx-dataview-controls" and the background color is using a variable called "$dataview-controls-bg". You could change that variable to transparent if you want to make the color transparent for all dataviews or you can create a custom class to apply to specific dataviews where you dont want the grey background.
If you make any changes in the sass files dont forget to recompile them. Heres a link to the documentation for setting this up with koala.
like Austin said,
It looks like something is messing with the dataview styling.
there is also this guide on how to use sass with gulp.