For your fronts the factory colours are grey and tan for front-left (tan is positive), dark green and light green for front-right (light green is positive), although there will probably be a connector, as you said, about two feet above the factory speaker where the colours will change to red and black for both doors. Black is negative and red is positive, and you can either use those wires or use your own wire and go up to where the connector is. I usually just de-solder the factory wires right at the factory speaker and solder those onto the aftermarket ones. For rears, I think you may want to go in there with a trouble light and re-check your colours.
Rear-left should actually be brown and yellow (brown is positive), rear-right is indeed dark blue and light blue (dark blue is positive). Try not to think of it in terms of power and ground for the speakers... The speaker's aren't actually grounded anywhere in the car; it's just positive and negative terminals. Even if you just guessed and had your positives and negatives swapped, all your speakers would still work, but they would be out of phase and you would notice the sound would be devoid of much bass response, on top of sounding "funny" in general. Good luck!