The colors are representative of information.
They are mostly for the benefit of the person developing for the hard drive.
Relays are sent rapidly through the cable. They alter the first available memory brick depending how many relays are sent. This changes the color of the brick, plus some toggling inside the events.
The read layer below, when prompted by a relay from the cable, uses projectiles to 'stimulate' the memory packet to fire projectiles back to it. The projectiles cause relays in the reading bricks which are sent out through the cable.
So simply put, relay > projectile > relay using color codes to organize the relay 'bursts'.
