Yes and no if the orange cap on the end made by the toymaker yes but it may not be removable.
Do you put a orange cap after you bought the gun example T-21 no your lose your weapon.
I ask the police but what if i paint my BFG orange the whole gun ,they could not tell me what will happen :o
If i paint it orange it does not look like a real weapon i said to them,yes but your T-21 is build on lewis gun so its doubtful.
I think when i have a troop in the netherlands i take a supersoaker and when i am on troop in belgium en gemany i take my BFG,sad but i think the best way to do i don't want to lose my BFG.