Chromatic Dragon Skeleton

Undead Nature.  The dragon doesn't require air, food, drink, or sleep.

Multiattack.  The dragon can use its Frightful Presence.  It then makes three attacks: one with its bite and two with its claws.

Bite.  Melee Weapon Attack: +10 to hit, reach 10 ft., one target.  Hit: 17 (2d10+6) piercing damage plus 4 (1d8) acid damage.

Claw.  Melee Weapon Attack: +10 to hit, reach 5 ft., one target.  Hit: 13 (2d6+6) slashing damage.

Tail.  Melee Weapon Attack: +10 to hit, reach 15 ft., one target.  Hit: 15 (2d8+6) bludgeoning damage.

Frightful Presence.  Each creature that is within 120 feet of the dragon and aware of it must succeed on a DC 16 Wisdom saving throw or become frightened for 1 minute.  A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.  If a creature's saving throw is successful or the effect ends for it, the creature is immune to the dragon's Frightful Presence for the next 24 hours.

Breath Weapon (Recharge 5-6).  The dragon exhales acid in a 60-foot line that is 5 feet wide.  Each creature in that line must make a DC 18 Dexterity saving throw, taking 54 (12d8) damage on a failed save, or half as much on a successful one.  The damage types depends on the color of the dragon chosen; black = acid; blue = lightning; green = poison; red = fire; white = cold.  

The dragon can take 2 legendary actions, choosing from the options below.  Only one legendary action option can be used at a time and only at the end of another creature's turn.  The dragon regains spent legendary actions at the start of its turn.

Tail Attack.  The dragon makes a tail attack.

Wing Attack (Costs 2 Actions).  The dragon beats its wings.  Each creature within 10 feet of the dragon must succeed on a DC 16 Dexterity saving throw or take 13 (2d6+6) bludgeoning damage and be knocked prone.  The dragon can then fly up to half its flying speed.