Hello Ali ,
Generally the styles used in our themes are theme specific. As described in the previously referenced thread you need to edit the cell template and change the background of the cell when it goes to Current state. The same is valid in case you have to predefine the appearance of the selected cell.
In our online documentation you will find a help article, which might be of help on this topic, please follow this link. In your case you have to get the style for Metro theme and change it in the way you need. You may get access the files for all Telerik themes from the Themes folder of your personal installation.
I am attaching you sample application illustrating this approach.
All the best,
the Telerik team
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