Fixed gradient color bar

Hello,everyone
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).
!0a32d749995ad3964d9f2975b600e5c894178c5a_1_690x392
Waiting for your help,Thanks!!

You can do that with a conduit. See i.e. https://github.com/mcneel/rhino-developer-samples/blob/6/rhinocommon/cs/SampleCsCommands/SampleCsDrawViewportLogo.cs