Hi @Artur Bogusławski ,
From the data sample, the data you want mark color is used in the matrix.
I don't think it's possible to meet the requirement from SSRS side.
If you are using the table, we could easily meet your needs in background color with "=IIF(Fields!Column1.Value = Fields!Column2.Value,Nothing,"yellow")".
With matrix data, it seems there is no method to solve the issue.
You may need to change the framework of your report or abandon your needs.
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