Yeah, that does look a bit in the range of 470 or 445, as well as tv could reproduce color at the TOS era.
I'm more of TNG era guy though, and to me star trek phasers have always been sort of orange - both the handheld ones and the ones used on ships. Afaik they have been this sort of color even since, both in tv series and movies.
I have no idea when that change was decided on, but in star trek i associate orange phasers with friendly fire and various other colors with enemy fire - often green (klingon, romulan, borg) or perhaps something like purple (cardassian?). I think they did it so it's easier to the viewer to differentiate friendly from enemy fire when watching the show and all it's spin offs etc.
I'm sure there are plenty of exceptions to be found to this, but in general i'd think an earth/alliance shot is orange, and any other color is enemy - except perhaps when fighting the borg and the alliance phasers rotate through a rainbow of colors to prevent them adapting to them or something like that.