I cold think of a few ways, but here's one using the family picking trick:
http://dl.dropbox.com/u/529356/TempPics/greenflash.cap
v0.99.84
The green sprites are in the Green family, which is then used to distinguish between instances of the same object. Any questions feel free to ask.
It works, and this is somewhat unrelated, but if you change the target from the overlap from the green family to GreenSprite, the game crashes. Why is this? Families work here, but I don't know why they do.
On a side note, this is the one thing I dislike most about Construct. I personally find the event system hard to use when you have many of the same object, such as in this instance. You used a family to solve this problem, but why did it work? If I needed to do this myself, I would have ended up doing it the way I told you above, and resulted in a crash. Next, I'd try all kinds of craziness with private variables and whatnot, but some things in Construct just don't seem intuitive to say the least.
This coming from an old Gamemaker user, so needless to say, I'm used to each object working independently without having to work out which ones will be affected by the global event sheet. Construct is so much better in so many ways, but manipulating individual instances is hard for me to wrap my head around with the event system controlling everything.