Maybe they got tired of the "black rifle" stigma? I like my black one better though. I also wonder if they are fully functional live fire weapons or like the blue dummy mags you can get for your Glock.
Dummy gun. That blue color is typical of resin dummy guns. I see them all the time at the local shows, mostly with dealers that sell the tactical slings for demonstration purposes. You also see them in handguns for the grips and external laser dealers.
At first I thought it was a training rifle upper used with the military/SWAT team for training.
These rifles use SIMUNITION or a special type of paint ball ammo that simulates a real M4 shooting. This allows the participants to engage in realistic training and suffer the results of their mistakes.
The blue color ensures that no one tries to shoot a real 5.56mm in the rifle.
After a second look I agree that it is a dummy/training rifle. Completely inert.