When a curve profile display is first created the field being displayed is by default colour modulated by the first field in the database. To disable colour modulation:

1. Right mouse click on the Curve branch in the workspace tree and select Properties from the pop-up menu that appears.
2. In the Curve Properties dialog that appears select the Line Style tab.
3. Click on the tick box for Modulate Line Colour to disable this option.
4. Click Apply or OK.