Which is correct?

This is a sample: it was made up in three seconds.

This is a sample: It was made up in three seconds.

Also, how many spaces should go between the colon and the next word? I was thinking two, since the clause after the colon is independent, but I'm not sure. Help please!

If the sample is a complete sentence, the capital will be better. However, I would suggest putting the sample within quote marks.

This is a sample: "It was made up in three seconds."

The older standard was two spaces after colons and periods, but since computerization, newer standards indicate only one. I decided to change to the newer, more current, standard.

I hope this helps. Thanks for asking.

Thanks!

You're welcome!

Both of the provided sentences are correct, but they are punctuated differently.

Sentence 1: "This is a sample: it was made up in three seconds."
Sentence 2: "This is a sample: It was made up in three seconds."

In sentence 1, the pronoun "it" is not capitalized because the clause following the colon is grammatically dependent on the previous clause. This means that the second phrase is not a complete sentence on its own.

In sentence 2, the pronoun "It" is capitalized because the clause following the colon is an independent clause, which means it can function as a standalone sentence.

Regarding the number of spaces between the colon and the next word, there is no universal rule. However, it is common practice to use one space after a colon. Some style guides, such as The Chicago Manual of Style, suggest using a single space.

To summarize:
- If the clause after the colon is dependent, you do not capitalize the first word unless it is a proper noun.
- If the clause after the colon is independent, you capitalize the first word if it can stand alone as a sentence.
- Use one space after the colon.