Correct sentence:
Chameleons change colour to show how they feel, to help warm or cool their bodies, or to hide.
Why this is better (easy steps):
- We say "how they feel" instead of "their mood" because it is easier for a young child to understand.
- We say "to help warm or cool their bodies" to make it clear we mean body temperature.
- We keep three reasons and separate them with commas. The last comma before "or" is fine but not required.
Short note about spelling: You used "colour" (British spelling). That is correct. In American English it is spelled "color." Both are okay.
Example: If a chameleon is cold, it might turn darker to soak up heat. If it is scared, it might change colour to hide.