herald of the orange light

can herald of the orange light discard effect from hand negate the effect of an opponent's ally the justice catastor destroy effect when it attks a marshmallon on my side of the field?

Sure why not

If the effect starts a chain, then yes. In this case, AoJC starts a chain, so yes you can activate his effect.

The effect of "Herald of Orange Light" can also be activated during the Damage Step.[1]

thanks very much!