It is not possible to have a shared legend across charts. But I can suggest two workarounds.
Option 1: Assign custom color to each dataPoint and render legend in a separate div yourself
Option2: This is kind of a hack.
1. Create multiple charts and don’t display their legend. You need to assign custom color to each dataPoint yourself.
2. Render an additional chart with legend enabled and hide the chart itself. Here is a demonstration of what I meant.