This is the first thing you do when working on a Solaris machine, if you don't want to get a headache. It is, in my experience, almost always possible to get more out of your graphics card and monitor.
Also, this helps preventing those ugly coloureffects you will get with the standard 8-bit colours configuration, as soon as you start up a couple of applications that together need over 256 colours, such as Netscape and some Java stuff, such as printmgr in Solaris 9.
Depending on the type of graphics card you have in your Sun, you need other tools for configuring it. Luckily, Sun doesn't have an elaborate selection of graphics cards, so you can even trial and error if you don't want to look it up.
The following is an overview of config programs:
This is also in the Handbook for Sun Frame Buffers at http://docs.sun.com.
Normally, any user can run this command and thus change monitor and graphics card settings. It is located in /usr/sbin.
The following command lists the resolutions supported by your graphics card and monitor, and the one currently in use:
your_prompt> m64config -res '?'
The question mark is in between single forward quotes.
Most default installations at least support this setting:
your_prompt> m64config -res 1152x900x76 -depth 24
Try higher resolution if you have enough memory, refer to output of resolutionlist. A higher colourdepth prevents non-active windows from being dithered in that ugly shade of rose and green.
If you get stuck while trying to find the best possible combination, pkill -HUP Xsun.