For example, if you have some coloured boxes:
In the Selection dialog select DarkOliveGreen and Maroon as the colours.
The components which are DarkOliveGreen and Maroon in colour are selected.
If you right-click Colour in the Selection filter and select Exclude from the context menu:
The components other than DarkOliveGreen and Maroon in colour are selected.
The representation in the Selection filter also changes to have a cross by them, 
.
