Hi,
This cannot be easily done in the current version, but it is planed in a further one (certainly version 2) when implementing table containers within reports. What can eventually be done in the current version is creating your own grid with containers: each cell would be defined by two embeded containers of the same size, setting a background color on the outer one. There are other similar tricks, but I won't suggest such solutions, because the report may become unreadable and difficult to maintain.
Best regards,
Romain