Went into compatability mode, changed it to 8-bit (256 colors),just like the the thing says. But everytime I start up the game, it doesn't start, and says something along the lines of "jedi knight requires that you play with a minimum of 256 colors" then just closes on me. Why does it keep telling me this obnoxious message, and how can I fix it? Thank you very much in advance to anyone willing to lend a friend a hand!

I play on win 10, by the way, and I've got it set to xp pack 2, run as administrator.

Turn off ALL compatibility options (both the overall compatibility mode, as well as all the detailed checkboxes).
It helped me.

I have the same problem. Yesterday I could play the game without problems.
I have Win 10 and I can't set the settings of the game to 8-bit.

Try dgVoodoo.

http://dege.freeweb.hu/dgVoodoo2.html

The message you get is misleading.
You are NOT supposed to set it to 8-bit.

Windows 10 users have been reporting a lot of errors that say "requires at least 256 color mode". I've seen a lot of gobblety-gook solutions that seem to only apply to installing from disk and only apply to certain video cards, and only apply to windows 7 or 8.

The actual solution for me (windows 10, NVIDIA card) was to select "run as Administrator" and "Reduced Color Mode 8 bit 256" in compatibility settings. However this came with complications.

Symptoms
First, the game runs normal for me on first install. After a few times of opening and closing the application I get this error. Reinstalling will fix the error for a few times running the game. Fortunately you can keep your saves when you uninstall. However, this is a crappy solution.

The error is a blank screen followed by the "requires at least 256 color mode" dialog box. My desktop resolution gets set to a really low value and stays until I run a different game. Very odd indeed.

Complication
When trying to run the automatic compatibility troubleshooter, the compatibility settings are incorrectly set to 16bit 65,536 color mode and can never be changed. The reduced color mode drop down is grayed out an uneditable.

Work Around
Make a copy of the JK.EXE application in the same directory. Rename it something different (i.e. jk_copy.exe). Right click, select Compatibility tab, and set the reduced color mode to 8bit 256 color mode, and select run as Administrator.

Replace all of your Jedi Knight shortcuts or change them to point at this new EXE

Many tutorials have recommended adding -windowgui to the shortcut target. This didn't seem to do anything for me, but others might have more luck.

I had the same problem under Windos 10. For me, it help to made a copy of my player directory, delete it and then to start the "Verify/Repair" under the "more" and "manage installation" of the Galaxy client. Afterwards it worked again.