Arnaud got a pass from Craig Rocastle and the Kansas City captain dribbled in alone, firing a shot inside the right post from 12 yards out that beat Rapids goalie Matt Pickens.
The tie gave the Wizards (4-8-4) a road point for the second straight game.
The Rapids (6-4-5) got the equalizer from Conor Casey in the 74th minute.
Though getting a point for the tie, Colorado remained winless for a fifth straight game.
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