question about colors

[Tian Qing]

Hi,

I have a question about the image color within GRASS.

I tried to compose  a color spot image with 20 level colors,
it finished,  but I couldn't show it.

I tried to compose it  with 256 level colors,
it couldn't finish in 3 hours.

Is there a limit for the color level to compose color
image within GRASS? at most 10 level?

My computer is Silicon Graphics workstation. It supports
16777216 colors( 24 bit).

Thanks a lot.

Tian Qing