The color is a tad different, but really quite close...  Also, I have seen, most colors will look closer to the center of the visible spectrum the higher the output, i.e. a 445nm while 900mW, (very bright), looks sky blue, (almost tourquoise), but when at 1-25 mW it looks half way from blue to violet...  & a very bright HeNe looks more orange while a dim one looks more red but is exactly 632.8 nm anyway...   so, I see this come into play in 593.5nm as a 20+ mW looks closer to 589nm than one doing 1-3 mW.  
    And I think it would take a lab 593.5 to do more than about 45 to 55mW at least for many seconds...   

   -Glenn