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.
the Telerik team
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