Custom colormap for fill3 function

I'm working on a finite element code using triangular mesh elements. After I obtain the solution to the system, I'm plotting the FEM solution by looping over all of the triangles and using the fill3 function. I want to assign a colormap afterward so that the largest z-axis value corresponds to red and the smallest corresponds to blue (kind of like 'surf').

I'm not entirely sure how to do this since the fill3 function takes in a color argument...