i am not able to select a row and change its color
Hi @Amrutha_Poojary,
Have a look at this demo for single row selection:
To change the colors you can use the respective CSS variables. You can use the browser's devtools to inspect elements and find the desired variable:
<RadzenDataGrid Style="--rz-grid-selected-background-color: purple; --rz-grid-selected-color: white;" ... >