My ship has limited power. So I am creating three bus paths: Ground, 5V, and 3.3V.  It will also help with the limited amount of wire I have.   It is important to not have ground loops.  Ground loop is an unwanted electric current path in a circuit resulting in stray signals or interference, occurring, e.g., when two earthed points in the same circuit have different potentials.  The 9V-1A power supplies share the same ground.   If you follow each ground path, they end without connecting back.   I made sure both sides of each bread board are grounded

Green: Ground
Red: 5V
White: 3.3V

I will keep 5V and 3.3V isolated on the control boards. Still need to connect up the 3.3V. I will also not to create loops.  Ground loops are very bad. 

Stardate 98775.72
I connected the ground and 5V buses together around the control boards.

Green: Ground
Red: 5V

I2C uses SDA and SCL connections. 
SDA: Serial Data: Data moves here
SCL: Serial Clock: Clock sync here

Mega 2560:
SDA : pin 20
SCL: pin 21

Hero UNO:
SDA: pin A4
SCL: pin A5

I checked each ground and power path with a multimeter to verify wiring.   I split the power connections of the Arduino devices to separate locations on the boards.  5V is reading 4.99V.   I checked for ground loops.  I also wired to limit the connection lengths. 

The bottom rows are I2C bus.  On the control board by the Slave 4, You will notice some extra jumpers.   I found that one of the control boards top and bottom rows were no longer connected left side to right side.   I place jumpers on them to complete the circuit.  I can now get 4.99V across the top row of red pins. 

I was able to find a few SN74HC595N shift registers to connect the lighting up with.  This saves on wire and ports of the controllers. 

I found a 8 position dip switch.  I need to find a shift register for them.   

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