Yes our boats do comply with ABYC wiring codes, and in the Marine world Black is ground, and there is no ground at the Ign. switch
If you look closely to the back of the switch there are markings:
B - for Batttery - red wire (hot)
I - for Ignition - Purple wire feeding Ignition and anything else that needs to come on with the engine
S - for starter - yellow wire w/ red trace stripe
A - for accessory - typically orange and feed stereo or speed control, this is hot in both I or A position, if you want to do programming you could turn the key back and program without having the ign,. on
Your fuse block will have a section with all the black wires connected, use this ground block to attach your ground.