How can I delete a color scheme or transfer a color scheme between computers?

Built-in vs. user-defined color schemes

Built-in schemes are indeed built-in, and cannot be removed. Read on to learn how to delete or transfer a user-defined color scheme. 

WIndows, Prism versions 3 and later, or Mac Prism 3 or 4: Delete all color schemes or transfer all color schemes at once. 

Color schemes are stored within Prism's preference file.  It's name and location depends on which version of Prism you use. Once you locate the preferences file, you can then copy it to other computers running the same version of Prism (on the same platform, win or mac). While Prism transfers most information from the preferences file from from older versions, it cannot transfer color schemes from version 4 to newer versions.

The preferences file also contains options set in the Preferences dialog, some settings made elsewhere in the program, user-defined equations, and the list of recently used files. It's all or none. If you want to transfer the color schemes, you'll also transfer the other stuff. Most people don't care much about any of that other stuff, but some people do.

Mac Prism 6: Each color scheme is stored in two files you can delete or transfer

Each color scheme is stored in up to three files. 

    ~/Library/Application Support/GraphPad/Prism/Common/ColorSchemes/<ColorSchemeName> (no extension)

    ~/Library/Application Support/GraphPad/Prism/6/Panel Color Lists/<ColorSchemeName>.clr   

    ~/Library/Preferences/com.GraphPad.Prism.colorSchemes/<ColorSchemeName>.clr

The first of those files is used by Prism within color schemes.

The second lets you choose a color scheme as a palette within the Mac color picker (within Prism).

The third one serves the same purpose, but is only present if created by Prism 5 (but Prism 6 can  read that file). 

To delete a color scheme, delete all the files that are present with the color scheme name, then restart Prism.

To transfer the color scheme to another computer, you only need to transfer the first file (Prism will recreate the second automatically). 

Note that there are at least two Library folders on your Mac drive. The squiggle symbole (~) means a user folder (named as the user name) inside the Users folder. The Library folders in the User folders are distinct from the Library folder at the top level of the folder tree. 

Mac Prism 5: Each color scheme is stored in its own file you can delete or transfer

Each color scheme is stored in its own file. 

    ~/Library/Preferences/com.GraphPad.Prism.colorSchemes/<ColorSchemeName>.clr

To delete a color scheme, delete the file, then restart Prism. To transfer the color scheme to another computer, transfer its file. 

Note that there are at least two Library folders on you Mac drive. The squiggle symbole (~) means a user folder (named as the user name) inside the Users folder, which is distinct from the Library folder at the top level of the folder tree. 

Win or Mac: Transfer color schmes one at a time without deleting files

Another way to transfer color schemes is to create a Prism file with a bunch of graphs, and apply a different color scheme to each graph. Then open this file in the other computer, go to each graph in turn, and bring up the Color Scheme dialog. It defaults to the colors of the current graph, so you can create a "new" color schemes fairly easily that matches the ones you created before. This approach is a bit more tedious, but doesn't mess with the settings in the config file.