HD2 Body Parts
All armors will come with a various amount of body parts that you will need to mod in order to properly port your modded armor into the game.
Male and Female Parts
Every armor set will come with Brawny and Lean body parts, or Stocky and Slim body parts respectively. Some armors when imported will automatically label these parts for readability. We will just call these Male and Female parts.
Depending on what you what body type you intend to modify, you will need to figure out which part is which.

Most armors will have a label that will tell if it is a male or female part.


However, some armors will not have this specified header. For example, take this B-24 shoulder piece.


In this case, you will need to look at the meshes and see which one is bigger than the other. Typically the larger one will be the male piece.

Only certain body parts will have male and female counterparts. This list is as follows:
Arms
Shoulder Pads
Chest
Connections
Waist
Thighs
Chest Accessories
Hip Accessories

INFO
Shoulder pads, thighs, chest accessories, and hip accessories will not be available on all armors.
Connections are any parts that have a neck and/or lower back mesh. Sometimes there will only be a neck mesh and no lower back.
Shared Parts
These body parts are shared across both body types.

Multiple armors will also have body parts that are shared with each other. One of the worst examples of this is the B-01/CW-4 family.

Similar colors means that those specific body parts are shared across those armor sets. You can view this spreadsheet by clicking on the Archide IDs button in the SDK modding menu.
This is something you may want to take note of when modding a specific armor set.