Choose the correct item. If you ... blue and red, you get purple.

My thought process:

This is a question about grammar, specifically verb conjugation. The sentence describes a general truth or a consistent outcome. In such cases, we use the present simple tense.

Let's look at the options:

• mixes: This is the third-person singular present simple form. It would be correct if the subject were singular (e.g., 'He mixes blue and red'). However, the subject here is 'you', which takes the base form of the verb in the present simple.
• mix: This is the base form of the verb. When the subject is 'you', we use the base form in the present simple. 'If you mix blue and red, you get purple.' This fits the context perfectly.
• mixed: This is the past simple or past participle form. It's used to describe an action that happened in the past, not a general truth.
• would mix: This is a modal verb construction, often used for hypothetical situations or polite requests. It doesn't fit the context of a general statement of fact.

Therefore, 'mix' is the correct choice because 'you' as a subject in the present simple tense requires the base form of the verb to express a general truth.

Ответ: mix