The 1st printing lacks the Unit Icon on the sticker, which was added for the 2nd printing onwards
makes no difference to play, just identification.
See the Light in this image, they have no Horn symbol, nor does the Heavy Cavalry have the helmet symbol
boardgamegeek.com/image/872949/commands-colors-napoleonics
here is some French cavalry with helmet symbol
boardgamegeek.com/image/3457728/commands-colors-napoleonics
I actually have a mix, and it makes no difference.
Otherwise the rules were slightly updated with each printing.
There are no 'editions' as such, the 3 printings are all 1st edition