The "Fire Perimeter Colors" dialog box allows you to select a fire behavior characteristic for displaying the fire perimeter.
The screen output of fire perimeters at the specified visible time step can be color-coded by fire behavior characteristics. The default is None, with perimeters drawn in white. The range of values and colors is set at 20 separate intervals calculated evenly between the maximum and minimum values for the visible time step.
If the fire perimeter colors are difficult to discern on your visible theme color background, you can either:
select the None option (default) to display solid white fire perimeters,
turning off the topographic shading,
re-run the simulation after changing the visible theme,
change the colors or brightness of the visible theme.