In the external file where we defined the colors, for each color keep also a character that will be used to display the menu:
yellow y blue b black k green g
When displaying the menu show: y) yellow z) brown b) black e) blue and wait till the user selects the appropriate letter. Allow the user to provide a color on the command line using the --color option and check if that is one of the valid colors. When reading in the file describing the menu options, check for duplicate use of the same letter.