    % scons -Q COLOR=Red foo.o

    scons: *** Invalid value for option COLOR: Red.  Valid values are: ('red', 'green', 'blue')
    File "/home/my/project/SConstruct", line 10, in <module>
    % scons -Q COLOR=BLUE foo.o

    scons: *** Invalid value for option COLOR: BLUE.  Valid values are: ('red', 'green', 'blue')
    File "/home/my/project/SConstruct", line 10, in <module>
    % scons -Q COLOR=nAvY foo.o

    scons: *** Invalid value for option COLOR: nAvY.  Valid values are: ('red', 'green', 'blue')
    File "/home/my/project/SConstruct", line 10, in <module>