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