What is the difference between light and dark blue in Chrome network tab

I'm experiencing a problem where requests (clicks on internal a hrefs) get stuck in pending state. Then when the page does respond, I see in the network tab the pending task divided to light and dark blue. Like this:

What does the light blue actually mean? Does this mean it was stuck at the client side for the light-blue time, or might it be that the request was stuck at the server?