Final answer:
The four adjectives in the sentence are small, bitter, Colombian, and generous.
Step-by-step explanation:
The sentence 'Mr. Walter took a small sip of the bitter Colombian coffee before adding a generous amount of sugar.' contains four adjectives: small, bitter, Colombian, and generous. Adjectives are words that describe or modify other words, typically nouns. In this sentence, 'small' describes the size of the sip, 'bitter' describes the taste of the coffee, 'Colombian' relates to the origin of the coffee, and 'generous' describes the amount of sugar added.