how to get more colours

[Suprit Kumar <suprit@xxxxxxxxxxxxx>]

hi  ferreters

I am very new to the ferret and need some help.

i am plotting a topography map from ETOPO2 data set over land area .
by using the SHADE/LEVEL=(0,2500,25) command .

the problem is that the colours in the map or colour key I am getting is not 
satisfactory, only  six colours are  being displayed , so the finer details 
of the topographiacal features are lost. ( like  there is hardly any 
difference between 200 to 500 meters level).

can anyone tell me how to get more colours for getting finer vertical 
resoulation?
i am using  ferret v5.41 on my PC ( red hat linux 7.2)

 thanks in advance        
 
bye
suprit