You can specify foreground and background colors for portions of the text. Under Text Properties, there is a submenu for specifying the foreground color, and a submenu for specifying the background color. Each one lists all the colors that you have used in Enriched mode in the current Emacs session.
If the region is active, the command applies to the text in the region; otherwise, it applies to any immediately following self-inserting input. When Transient Mark mode is off (see Persistent Mark), it always applies to the region unless a prefix argument is given, in which case it applies to the following input.
Each of the two color submenus contains one additional item: ‘Other’. You can use this item to specify a color that is not listed in the menu; it reads the color name with the minibuffer. To display a list of available colors and their names, use the ‘Display Colors’ menu item in the Text Properties menu (see Editing Format Info).
Any color that you specify in this way, or that is mentioned in a formatted text file that you read in, is added to the corresponding color menu for the duration of the Emacs session.
There are no predefined key bindings for specifying colors, but you can do so with the extended commands M-x facemenu-set-foreground and M-x facemenu-set-background. Both of these commands read the name of the color with the minibuffer.