Introduction
The Macintosh Palettes tab is mainly informative. It displays the three system palettes used on the Macintosh. Against what is done in Windows icons (*.ico files) or more generally in Windows bitmap files (*.bmp files), Macintosh icon files in 16 and 256 colors (4 bits/pixel and 8 bits/pixel) don't contain their own palette, but refer the Macintosh system palettes. There are three such palettes:
16-Color Palette
Special Icon Palette, going to 32 + 2 colors
256-Color Palette
Naturally, this last one is the only one of interest nowadays, because of the evolution of the display hardware (who still displays in 16 colors?). Having this palette at hand may help you to understand how and why an icon, pleasant on a PC, can fade on a Mac, or the other way around.
All three palettes can be copied to the clipboard with the CTRL C command when they are displayed. You can then use the eye-dropper to select the colors you want to use.