Apparently, the Blue/Red knob in-between the vents is not for Cold/Hot.
The Blue side is to let ouside air in, while the Red side is inside air and only works for the front vents only. Not feet or windhield vents.
The example I was given was in the winter time, if you have the heat on your feet or windhshield, keep the knob on blue and it'll take air from the outside and blow through the front vents.
Not be to be confused with the re-circulate button