I really wanted to like this, but I think that colors preferences are both subjective and born of habit/experience which leads to wiring our brains to expect certain colors for certain things, because I don't like pastels, and I don't like red as a non-alert color.

It's a good idea, with a lot of thought put into it. The author should keep trying. Maybe there is more than one right option.

Personally, I think the best way to do this is by a "hot or not" site for fonts and colors. Have a page for each language with "hot or not" of random fonts and color combinations until the stats show which combinations certain groups like. Tie in other surveys as well and give away gift certificates to Amazon each month as a prize for over 100 votes that aren't outliers.

There does seem something common about themes that appeal to many people but ultimately each has their own correct version of how things should be. Hence my next project https://github.com/chriskempson/base16 Interesting idea by the way!