Range mode uses RGB sliders to separate colours. It is useful for separating keylines and creating initial masks of defined areas.

1. Make the image active and choose Separate Menu > Spot.
2. Choose Range from the pop up menu and pipette a colour from the design using the Pipette Tool.
   
3. Press the New button to create a Range colour.
4. Make sure the Preview and Tonal buttons are checked. The design will disappear and a preview of the separation will appear as you alter the sliders.

   

5. Create a little distance between each set of markers on the min and max sliders (the further apart you pull the sliders, the more of the preview you will see).

Adjusting the sliders changes the two halves of the colour in the Spot Window. The two halves of the filter colour represent different parts of the separation.

When you separate the design, you are aiming to keep the two halves of the colour quite close to the original colour you chose with the pipette. The two colours displayed show you a preview of the type of colours being separated. The closer you keep them to the original, the more specific the separation. 

Try changing the sliders so that the colours are very different to the original. Notice that the preview changes dramatically.