Only for AR.Net Web Designer.
You will need to go onto a report and follow these steps to get an alternating line style on your table.
Click on table object and select just the table.
Go to Style under Layout.
Select a style. This will be based on the theme of the document.
Add this to BackgroundColor:
{IIF(RowNumber(Nothing) Mod 2, Theme.Colors(1, 4), Theme.Colors!Light1)}
Edit for the specific colors you need.
Logan McCarthy