Hello Julian,
The default background of GridViewCell is set to Transparent, in order to display properly the visual elements that are place behind it (i.e. row's "select" and "over" borders). I have prepared an example project that partially solves your issue and I have attached it for your reference. Unfortunately an alternative approach won't be possible without serious modifications in GridViewRow/GridViewCell template structure. Please, let us know whether this is an appropriate solution for your case.
Regards,
Ivan Ivanov
the Telerik team
Explore the entire Telerik portfolio by downloading the Ultimate Collection trial package. Get it now >>