from typing import List


def _apply_SEAR_3(question_tokenized: List[str]):
    """
    SEAR 3: color -> colour
    """
    output = []
    applied = False
    for token in question_tokenized:
        if token == 'color':
            output.append('colour')
            applied = True
        else:
            output.append(token)
    return " ".join(output) if applied else None