See the attached sample where i give condition to the straight table which gives the null value highlighted in the red background by sinple condition to check null values. It is a chart which display the null values in any data.
Didn't get your question properly. You want the related data to be highlighted ? if so it is already highlighted by "Related item for the selection are in White" and data which is "Unrelated to the selection are in Gray"
When I last asked this question, I received a response that you cannot change QlikView's default selection colors (white for possible, gray for excluded, green for selected, blue for locked), and the same thing appears in QlikView 10's help file. You can play with the shades of these colors using the preset themes, but that's it.
What you might be able to use here is a List Box expression, perhaps set up as a stoplight gauge (see below image for example). This was achieved by adding a listbox expression with the formula along the lines of If(count(distinct myColumn)>0,1) and a stoplight gauge with a single light set to yellow.