So I took a closer look at Mass Effect 3's new “Reputation System”. According Bioware, the Reputation System solved Mass Effect 2's Dialog problem, By committing to either Paragon or Renegade Dialog Options to pass the Skill Checks to unlock the Special Colour Coded Dialog, deviating from the committed path will leave you a few points shy of passing the skill check because Paragon and Renegade are two completely attributes and the game doesn't offer enough side quests to fill up both attributes.
Mass Effect 3's Reputation System circumvents this problem by simply linking all your choices to a single attribute, Reputation. So in theory, you're free to to resolve conflicts in either paragon or renegade methods without worrying about not having enough Reputation, oh and and theres neutral options that yield Paragon/Renegade-less Reputation. I played through Mass Effect 3 only once, without dialog grinding, so I had no reason to suspect the system didn't work in practice.
But it turns out there is a tiny little flaw in the system. I, like many other people, assumed that the only attribute you needed to pass the Skill Checks was Reputation, but thats not the case. You'll still Find yourself having access to the Red Dialog but not the Blue, and vice versa. Well, it turns out the “Skill Checker” (haha Skill Checker ! Its a Virtual Bouncer LOL :) !) has a filtering mechanism. A “Ratio System” if you will.
So heres how I think it works, when you start the game you have 0 Reputation, however, your Paragon-Renegade Ratio is 50/50, so throughout the game as you make choices it increases your Reputation but when making a Paragon Decision it has a secondary effect, it readjusts the Ratio from 50/50 to 60/40 (or 51/49 or 55/45, it depends on the scenario), therefor If you want access to Blue Dialog, the “filter” only use 60% of your Total Reputation, and for Red Dialog it only uses 40% of your total Reputation.
Luckily this does not mean you have it commit to being Paragon/Renegade, leaving you no choices to make, like in Mass Effect 2 (Because Neutral Choices yielded nothing). It just means if you want Blue Dialog then you can't make any Renegade choices and if you want Red Dialog then you can't make any Paragon Choices, well actually you can, and if you do, just make sure you either have a lot of Reputation to compensate for the slightly balanced Paragon-Renegade Ratio. Or you can have less Reputation and a Paragon-Renegade Ratio of 99/1.
But it was worth a try right ?