Here is a clear, grammatically correct version of your sentence for an 8-year-old:
- Original: People can look very different: fair or dark skin, straight or curly hair, and short or tall.
- Corrected: People can look very different: fair or dark skin, straight or curly hair, and short or tall.
Notes:
- Use a colon to introduce a list that explains the idea.
- Keep the items in the list parallel: adjectives describing skin, hair, and height.
- There is no space before the punctuation mark in American English; the period goes after the closing quote or sentence.