In general, we prefer paired wire like red/black zip cord. It's got a soft pliable insulation that doesn't act like a spring and fine strands that bend and form easily. It's available from a number of places online.
We also like to use the smaller 30/45 amp Anderson Powerpole connectors. We've been using them in red/black combinations, but I saw a team this year use a number of colors to organize their wiring and it seemed to work well.
Proper crimp tools is often overlooked. We use the ratcheting tools (similar to the powerpole tool - in fact the dies can be swapped in the same tool) for crimp on connectors.
If you're using the 10-in-one tool that strips wire, cuts screws as well as crimps wire, you are asking for trouble. They simply don't produce a good crimp and will pinch your fingers as often as not.
Find the right crimp connectors to go with the tool as well. The ones with the hard slippery plastic shell that come in the KOP are awful. We throw them away so that they don't accidentally get used.
I've collected a lot of sources for handy things for robotics
here