Controlling on the color of the result.

Prime does not support doing so. In old Mathcad we could achieve something like you demand by using scripted components, but Prime does not offer scripting.

There was a thread a while ago where it was suggested that the output text should actually be a cell in an embedded Excel sheet which of course could be colored depending on certain conditions. A quite elaborate solution for a simple problem, but at least it works.

See here: https://community.ptc.com/t5/Mathcad/Color-coded-results/m-p/862742/highlight/true#M205638

Unfortunately, PTC didn't think of copying Mathcad 15 features. So Mathcad Prime can't highlight results or intermediate results in any way. If you wish to see this feature in future prime releases then vote in Mathcad improvements; see here. Scripted Controls with Conditional Formatting - PTC Community

Maybe PTC will listen.