By default ag-Grid will display according to the provided theme you use (e.g. Balham, Blue, Blue etc.)
However you are able to style the rows in the ag-Grid using the RowStyles property of User Interface State.
The RowStyles array can take up to 3 properties: 'All' (which is used for all rows and will ignore other properties), 'Even' or 'Odd'; for the last 2 properties you can supply either, both or none.
In this example we have set an Even Row style (using a classname property - we need to make sure that we provide a css style of that name) and an Odd Row Style that uses the IStyleobject that we populate.