If we pick two respondents at random, what's the probability they both selected purple

This depends on what other colors are in the question. But put 1/x  and replace the x with how many colors there are and thats thier probabilaty of choosing purple.

Step-by-step explanation:

Theres no possible way of knowing unless you already have met and or know the person so if theres green, blue, pink, yellow, and purple, theres 5 colors and purple is 1 out of them therefore, 1/5