What do the colors mean on route map?

Okay, I think what I really want to know is, how does it decide what pace should be what color? What is that based on?

Hi

Line colour indicates your pace throughout the workout (green being fastest, red being slowest).

The Grey dots are likely where signal is lost and then reaquired.....

I’d say that the colour would be based on your average pace throughout the run, green when you were faster than average and red when you were slower

I brought my phone with me to a Spartan Race whilst wearing my Apple Watch 2.

How about when there are gray dots on the map? What do those dots mean?

I have these grey dots all through a 5.3 mile run? It shows my run to be 3.45 miles!

The dots are where the gps signal was lost so it tracks the distance like a pedometer until it reacquires the signal.