Cognos - Ungroup data in crosstab

Create a new data item(product&color) as Product||Color

Now place this data item in place of product. Then unlock report studio using lock/unclock button in top tool bar.

Then select the text item of this data item/node(please make sure only text item is selected not the complete node). And in the properties pane-> change the data source property to Product data item instead of product&color.

The output will be as:

A  WHITE 10
A  RED      3
B  BLUE    8