color depth

Hi all

I'm a new Linux user (from 1 year) and I must run some applications that 
run only with 8 color depth, but when they start I loose all the color 
resources and the monitor blink.

How can resolve this problems?

I trying to modify the xfree86config file adding two Screen section one 
with 8 and the other with 16 color depth, I changed also the ServerLayout 
section but I see only one Screen definition (8 color depth) and never changed.

Help me please, thank you in advance