Match certain parts of a mesh to the body? I'm trying to make Knight tassets, as show in the second pic. So I need the cream colored part of my mesh to stay to the color coded bone, the green colored part to the green bone and so forth so that the entire thing doesn't look so stiff when it moves. Been fiddling with it for like an hour and still can't figure it out. I took like a 2 week break from Blender and I think I sorta braindumped everything,

Any help? I've made vertex groups for each part of the mesh but can't figure out what to do next.
You need to assign the appropriate parts of the mesh to the appropriate bones like you would normally. Use the weight paint tool, or vertex grouping.

For those side plates I would definitely recommend assigning them their own bones if they are not strapped into the leg, and would, for instance, hang downward if the character leaned to one side.