Correct sentence: Chameleons change colour to hide or to show how they feel.
Is the original sentence okay? Yes — "Chameleons change colour to hide or show their mood." is understandable and mostly correct. Making it a little clearer helps young learners.
- Chameleons — this is the name of the animals (the subject).
- change — this is the action they do (the verb).
- to hide and to show how they feel — these explain why they change colour. Using "to" before both words (to hide, to show) keeps the sentence balanced and easy to understand.
Note about spelling: "colour" is the British spelling and "color" is the American spelling. Both are correct; choose the one you use already.
Short version to practise: Chameleons change colour to hide or to show how they feel.