Material Overrides allow you to edit materials inside complex/deep mesh structures like SVGs or Text. This can be achieved via the Sub-Mesh Behaviour's Fill or Stroke tabs.
When you add a Color Material Override to a Sub Mesh you can blend between the original color and the one you set. You can then, for example, connect a Falloff to the Sub-Mesh to control the effect.
Color - set your color using hex or rgb values (note - only rgb values can be animated).