- gray gray-levelprocedure
Returns a procedure which takes a single argument, a string, and which when called behaves as follows.
If ANSI escapes are enabled, the procedure returns a string consisting of its argument with a prefix that selects specified text color (obtained by calling the gray-escape procedure with the values of the gray-level argument) and a suffix that selects the default text color.
If ANSI escapes are not enabled, the procedure returns its argument.
The caller is resonsible for verifying that the terminal supports 256 colors.