This Bible contradiction is from the Skeptic's Annotated Bible.
On an ass and a colt.
Matthew 21:5-7 View context
Tell ye the daughter of Sion, Behold, thy King cometh unto thee, meek, and sitting upon an ass, and a colt the foal of an ass.
And the disciples went, and did as Jesus commanded them,
And brought the ass, and the colt, and put on them their clothes, and they set [him] thereon.
On a colt.
Mark 11:7 View context
And they brought the colt to Jesus, and cast their garments on him; and he sat upon him.
Luke 19:35 View context
And they brought him to Jesus: and they cast their garments upon the colt, and they set Jesus thereon.
On a young ass.
John 12:14 View context
And Jesus, when he had found a young ass, sat thereon; as it is written,