Does the following passage contain a colon error?

When Haruki was young: he didn’t think he’d be a famous author.

Yes, the passage contains a colon error. The colon should be removed or replaced with a comma since it is not necessary in this sentence structure. The correct version would be: "When Haruki was young, he didn’t think he’d be a famous author."

Yes, the passage contains a colon error. The colon is used incorrectly after "young." A colon should only be used to introduce a list, explain or elaborate on the preceding statement, or introduce a quotation. A possible correction for the passage would be:

"When Haruki was young, he didn't think he'd be a famous author."