When spectating a match it would be great if there would be something to show when a hero/wards/dominated creeps/remnants are visible to the enemy team.
With fog of war for both teams visible to spectators it can be difficult to know if one team can see a hero from another team.

Two solutions I've considered for this are a white(or other color not in use) bar in between the health and mana bar when seen or unseen,
or what I feel is a better option would be a white(or unused color) highlight to always be visible when the hero/ward/remnant is unseen by the enemy, by highlight I mean the red/green mouseover highlight for friends and foes