Does mirage mirror also copy +1/1 counters that are on a creature? Particularly ability counters ex: colossus of akros Would the mirrored copy copy with or without the counters if the original colossus was already in monstrosity mode?
A copy effect such as Mirage Mirror's doesn't copy counters of any kind (whether +1/+1 or otherwise) (C.R. 706.2).
A copy effect also doesn't copy whether a permanent is monstrous (C.R. 701.30b, 706.2). If Mirage Mirror isn't already monstrous, it doesn't become monstrous merely by becoming a copy of a monstrous permanent.
If Mirage Mirror becomes monstrous (e.g., because the ability it acquires from Colossus of Akros resolves [C.R. 701.30a]) while a copy effect is active on it, it doesn't stop being monstrous when that copy effect ends, when it becomes a copy of a permanent that isn't monstrous, or when it otherwise stops being a creature; rather, Mirage Mirror will "sta[y] monstrous until it leaves the battlefield" (C.R. 701.30b).
For the purposes of monstrosity, whether a permanent is monstrous does not depend on whether or not it has +1/+1 counters on it (C.R. 701.30a). See also this thread.
Copy effects work pretty much like Xerox machines: you get a copy of the plain card, as if you just picked it up from the table.
Nothing that happened to the original card gets copied… the only exception being other copy effects: those get copied.
For example, if someone were to copy your Mirror-turned-into-a-Colossus, they would get a (plain) Colossus.
Rule 706.2: When copying an object, the copy acquires (…) the values (...) printed on the object (...), as modified by other copy effects (…). Other effects (…) are not copied.
A copy effect also doesn't copy whether a permanent is monstrous (C.R. 701.30b, 706.2). If Mirage Mirror isn't already monstrous, it doesn't become monstrous merely by becoming a copy of a monstrous permanent.
If Mirage Mirror becomes monstrous (e.g., because the ability it acquires from Colossus of Akros resolves [C.R. 701.30a]) while a copy effect is active on it, it doesn't stop being monstrous when that copy effect ends, when it becomes a copy of a permanent that isn't monstrous, or when it otherwise stops being a creature; rather, Mirage Mirror will "sta[y] monstrous until it leaves the battlefield" (C.R. 701.30b).
For the purposes of monstrosity, whether a permanent is monstrous does not depend on whether or not it has +1/+1 counters on it (C.R. 701.30a). See also this thread.
Nothing that happened to the original card gets copied… the only exception being other copy effects: those get copied.
For example, if someone were to copy your Mirror-turned-into-a-Colossus, they would get a (plain) Colossus.
RULES OF MAGIC :
http://magic.wizards.com/en/game-info/gameplay/rules-and-formats/rules