An apparatus for displaying a plurality of data categories (104, 108, 114) each having a plurality of data subcategories, the apparatus comprising: a display with a current luminous output capacity that is configured to concurrently produce a first visual presentation of a first data subcategory and a second data subcategory of a first data category of the plurality of data categories and a second visual presentation of a fourth data subcategory and a fifth data subcategory of a second data category of the plurality of data categories; and a processor that is configured to control said display during said concurrent production of said first visual presentation and said second visual presentation to generate a transparency for the fourth data subcategory and the fifth data subcategory selected to provide at least partial visibility of said first and second data subcategories (140, 141) through said fourth and fifth data subcategories; characterised by that; said processor is configured to assign a luminance difference between the first data subcategory and the second data subcategory of at least 30% of the current luminous output capacity of said display, and such that for one of the first data subcategory and the second data subcategory a luminance greater than or equal to 90% of the current luminous output capacity is assigned; said processor is configured to assign a common luminance for the fourth data subcategory and the fifth data subcategory that is 30% to 60% of the current luminous output capacity of said display; and said processor is configured to assign a color saturation for the fourth data subcategory and the fifth data subcategory that is greater than 75%; said processor being configured to assign a lower color saturation to objects of the first data subcategory than to objects of the second data subcategory. a display with a current luminous output capacity that is configured to concurrently produce a first visual presentation of a first data subcategory and a second data subcategory of a first data category of the plurality of data categories and a second visual presentation of a fourth data subcategory and a fifth data subcategory of a second data category of the plurality of data categories; and a processor that is configured to control said display during said concurrent production of said first visual presentation and said second visual presentation to generate a transparency for the fourth data subcategory and the fifth data subcategory selected to provide at least partial visibility of said first and second data subcategories (140, 141) through said fourth and fifth data subcategories; characterised by that; said processor is configured to assign a luminance difference between the first data subcategory and the second data subcategory of at least 30% of the current luminous output capacity of said display, and such that for one of the first data subcategory and the second data subcategory a luminance greater than or equal to 90% of the current luminous output capacity is assigned; said processor is configured to assign a common luminance for the fourth data subcategory and the fifth data subcategory that is 30% to 60% of the current luminous output capacity of said display; and said processor is configured to assign a color saturation for the fourth data subcategory and the fifth data subcategory that is greater than 75%; said processor being configured to assign a lower color saturation to objects of the first data subcategory than to objects of the second data subcategory.