Fixed gradient color bar

Now I’am writing a FEM plugin in Rhino. And I have some problem on post-processing.
I have asked some question about: how to make a make face color map before.
Now, I have another question.Like the following figure, can you tell me how to add a fix gradient color bar in the Rhino Viewport (When moving the model in Rhino, the color bar is always fixed to the upper right corner of the Rhino Viewport).
Waiting for your help,Thanks!!

You can do that with a conduit. See i.e.