The settings dialog let's you configure JDraw. The settings are stored in JDraw's configuration file (<user-home>/jdraw<version>.dat).
This opens a small dialog that let's you specify how tolerant the fill tool will be. Enter the maximal values that a colour may deviate in its red, green, blue and alpha values to be replaced in the filling process. If all values are zero, the fill tool will only replace the colour that you click on.