That's what the study addresses (even if inconclusively).
The question is how "but they didn't include color blind people" has any relevance to the subject.
For color blind people we already know that they don't see the same colors, so the answer for them is trivial. They can't even decode the same input, so nobody expects them to have the same color qualia as someone who does.
The purpose of the study is to examine the color of people with same typical vision capabilities. So regarding the objection, it's like some team doing a pitch perception study and someone asks why the deaf weren't included!