Civilization II for Mac OS makes use of several picture files for its game graphics. The palettes for these picture files can cause problems for Mac OS based graphic editors because the first and last palette entries are not white and black. Because of this, some editors may modify the palette at some point so that the first and last entries are valid. They may accomplish this by overwriting the existing first and last colors, or by shifting the palette to make room at the start for white, thereby losing the last two palette entries when black is placed at the end.
Unfortunately, changing the palette like this will prevent Civ II from properly using the picture. Civ II expects to find certain colors at specific entries in the palette for the pictures. In addition, there are some pictures whose sole purpose is to provide Civ II with a color palette. What really complicates things is the fact that while the game is running, Civ II will construct a palette for use by the computer by taking specific portions of several palettes from different pictures.
In theory, someone could write a graphics editor that doesn't screw with a picture's palette, and perhaps one does exist that I'm unaware of. However, until that editor is created/found, you can use Civ II Pal to work around the problem.
Civ II Pal will temporarily change the palette of a picture file so that its first and last entries are white and black. This should allow you to edit the picture using any graphics editor, assuming the editor doesn't screw with the palette in some other way, such as reordering or reducing the color entries.
To use Civ II Pal, drag one or more picture files onto the application. This will create a temporary file with the same name but with a ".pal" extension. This file contains the real palette for the picture. When you're done editing the picture, drag it onto the Civ II Pal application again and it will restore the palette of the picture and delete the ".pal" temporary file. If no ".pal" file is created then either the picture already has a valid palette or an error has occurred.
This is by no means a perfect solution. There is a chance that when you're in the graphics editor you could pick a color to paint with that Civ II may ignore when it loads the picture for use. To minimize this possibility, use the eye dropper tool to pick colors from the existing artwork instead of picking one from the editor's color palette/picker. Also, since the first and last entries of the palette are changed by Civ II Pal, the picture will look different since the original first and last color entries are no longer available.
This is the same trick we used to modify the artwork when making changes for the Mac OS version of Civilization II. Hopefully this will make things a little easier when it comes to modifying the existing Civ II artwork when you're creating custom scenarios.
