Question

Which question could be tested in a scientific manner?
What causes some people to be color-blind?
Why should people be nice to other people?
Why is the color purple better than the color red?
What are the best shoes to wear when exercising?

Answer 1

The questions from this lot which could be tested in a scientific manner would be "what causes some people to be color-blind"
and
"what are the best shoes to wear when exercising"
Both of these questions can be tested in a scientific way through an experiment. 

Answer 2

The question, which can be tested in a scientific manner is this: WHAT CAUSES SOME PEOPLE TO BE COLOR BLIND.

For a question to be capable of been tested scientifically, it must possess some characteristics. The characteristics include the following: it should be testable, it should have real answers and it should be able to lead to an hypothesis, which can be proved to be wrong or right. Asking the right question is part of the methods that scientists used to investigate observed phenomenon.