Beyond making the Mirror's Edge world look like a giant Target commercial, the contrast between red and white serves a functional purpose. When something on screen is glowing crimson, it lets the player know this object is useful for maneuvering through the environment. The game calls this "runner vision." I call it a failed attempt at player guidance.
The justification for seeing red is this: it simulates how useful objects may stand out to a highly skilled runner like Faith. I reluctantly accept this explanation. Most games rely a similar excuse to account for weapons glowing, or any other attention getting device. However, when the creators shepherd me through an experience, I can't help but feel manhandled.

Dice studio saw fit to include one other directional assistance mechanic. With the press of a button, Faith can turn and look towards her primary objective. This was even more of an abysmal failure. The entire point of the game was to find a path towards a single location, a path that is almost never a straight line. Getting to a distant door or ladder is an action composed of many small steps. The immediate goal of finding the best route to move forward trumps the long term locational goal and makes this function essentially useless.

To carry this bicycle analogy one step further, needing this assistance at all is a sign the bicycle was not built with training wheels. You wouldn't need the developer's artificial touch if the game could be "ridden" on its own. Though Fable II's trail does not draw attention to itself the way red-vision does, it is still included to replace a coherently structured and easily managed level design. Perhaps Lionhead Studios removed a map display to clean up the HUD. Or arguably, the expansive free-flowing nature of Fable II makes an easily maneuverable experience impossible. Regardless, any guidance system exists when the ideal (the player leading themselves) cannot be met.
Of course in Mirror's Edge, and Fable II, I can turn this assistance off. However, in doing so, the whitewashed buildings, without the red contrast, lose some of their meaning and become more boring than they were to begin with. Effectively, seeing red is a less than perfect band-aid for other game flaws I hope to cover next week.
Again, I am no proponent of game difficulty for its own sake. I'll gladly accept a helping hand when appropriate. It is when this hand is wearing a ruby encrusted glove that glitters in the sunlight that I am inclined to let go.