Hi Marian,
Please try the following CSS script:
.sapzencrosstab-DataCellSelectData { background: #E6F2F9 !important;
}You will have to embed this class in a CSS file which you will then be required to upload to your application. Once you do this, you should be able to see selections that you are making, regardless of the exceptions that show up on the crosstab.
I hope this is what you were looking for.
(In case you require instructions on how to use a CSS file, please refer to this video)
Thanks and Regards,
Eshwar Prasanna