Print total rendering time after a long script of several image renders? This wouldn't be for animation, but variations in color and view angle for the same object. So all renders are on frame 1 (in case that matter).

It would just need to add together the rendering time of each images at the end of the script. I have no idea how to do just that though, and how to access the rendering duration info from python in Blender.
I think your question is a bit incomplete but usually the time module is used, then

import bpy , time

def yourFunction(self,context):

    start = time.time()
    ####your script
    ####
    ####
    stop = time.time()

    result = stop-start

    print("Your time is :"+"{:05.2f}".format(result)+" Seconds")


note "{:05.2f}".format(result) It is used to format the seconds by approximating the cent