Hi Luca,
I wrote a blog to use a Crosstab Object with Display Rules to get this solution:
See the steps here: VA Report Example: Use Display Rules to get diagonal coloring on a Crosstab
I hope this helps!
Thank you,
Teri
Teri Patsilaras is a Senior Manager in the Global Enablement and Learning (GEL) Team within SAS R&D's Technology Transfer and Governance Division