Answer:
When displaying the "Values on Surfaces" result values, there are two distinctions.
The result values are displayed either "On grid and user-defined points" or "On FE mesh points".
When displaying them "On grid and user-defined points", the results are displayed in the distance of the grid points.
The distance of the grid points is a property of the surface and can be controlled in the "Edit Surface" dialog box.
As an alternative, you can display the result values "On FE mesh points".
The number of the FE mesh points depends on the generated FE mesh size.
You can control the displayed color gradient by selecting the "Distribution of Internal Forces/Stresses" option in the Display navigator. See the FAQ below.