Slow down stepper motor's speed using stepper driver DRV 8825
Okay, turns out that there was an issue with a wiring too and the labeling was indeed incorrect on the motors. A big thanks to Andy for spending his precious time in assisting me. 

How I solved the problem

Update: After discussion with one of the commenters below, it is learned that there is no difference in the order of wires connected to the driver, therefore, the order of wires labeled in my question and in the answer below don't matter as much as setting the value on the variable resistor itself.

These drivers have an onboard tiny variable resistor that limits the current to the motor. I just had to tweak it to get everything working. Now the motor runs in ultra low speeds, although with some mild vibrations (in full step mode). 

After enabling the micro-step mode provided by the chip, I was able to dampen the vibrations by a huge margin and got everything working butter smooth.

For anyone else who may have this motor, here are some references:

Orange and Brown wires constitute one coil of this motor, with the black being the center tap.

Likewise, Yellow and Red constitute the second coil, with the white wire being the center tap.

The way you connect it to a Polulu DRV8825 is as follows:



I hope this helps anyone else who may have the same issue.

Cheers.