One of the goals in my game is "no wrong choice". Nothing leads to a game over screen. The only choices that eliminate opportunities for sex are the clearly marked "black choices" that "friend zone" you.
As for the red and blue paths, they offer different flavors of relationship. Your choices are cumulative, so as you build up stats in either color you'll find the story playing out in different ways. All roads lead to Rome, but it's up to you if you find an Empire or ruins waiting for you when you arrive.
I will say that in many cases, the blue path offers a more romantic and gentlemanly approach (not in all cases). So when playing a more "blue" approach, some of the "rewards" may take longer to play out, but they will involve deeper, more intimate relationships than the lust filled "red" path.
So folks on the blue path may need to exercise a little more patience, but do not doubt that great things come to those who are patient.