What I would suggest is going to the Point Styles tab of the Options dialog for the layer and setting up attribute-based styling using the Elevation/Depth attribute, then you can setup whatever coloring that you want. Use the custom dot symbols (i.e. custom size and color), that way the point color will automatically blend between the values that you specify (assuming that you want that).
Let me know if I can be of further assistance.
Global Mapper Guru