If you have two matrices and want to color map a surface plot using a second matrix, these two matrices should be in same matrixsheet as matrix objects.
If you have XYZZ data, want to plot a 3D surface and set the second Z as colormap, you need first convert these two Z data to two matrix objects in same matrixsheet.
Activate the matrixsheet or select required data from worksheet.
From the menu, choose Plot > 3D: 3D Color Map Surface.
Click the Color Map Surface button on the 3D and Contour Graphs toolbar.
(Installed to the Origin program folder).
The Z values determine a surface of X and Y grid lines and fill color from a color map.