Since the new footer was put into place I have started using the "all sites" dropdown pretty much exclusively to navigate through the sites. Some days, I just want to go through "my" sites looking at new questions. Other times, I want to see how my questions, answers, or comments have fared.
Surprisingly, I'm able to remember my rep on the dozen sites where I'm active. If I arrive and see my rep is 398 instead of 386, I can hover over my name to see what happened. But there are sites where I don't notice that my rep has changed until some time after the fact.
I think there's room in the list of sites for a number to show any rep changes - to be based on a timestamp or a "you saw this" that works just like the inbox and notification numbers, or possibly to just be "today" if that's less coding.
I would probably prefer showing blanks where you have no change, and it doesn't need to be red, I just did that to make it stand out.