If a Monument has any +1/+1 counters on it, those counters will remain on the permanent after it stops being a creature. Those counters will have no effect as long as the Monument isn't a creature, but they will apply again if the Monument later becomes a creature.

Activating the last ability of a Monument while it's already a creature will override any effects that set its power or toughness to a specific value. Effects that modify power or toughness without directly setting them to a specific value will continue to apply.

Each Monument is colorless, although the last ability will make each of them two colors until end of turn.

A Monument can't attack on the turn it enters the battlefield.