I'm pretty sure this works, but not sure how accurate the readings are.
It only works for Windows (maybe there's something similar for Mac/Linux, but I don't know how to do it). I'm also not sure if Windows 7 has this feature.

1. Open Task Manager and click the "more details" expansion.
2. Click Performance tab, then open Resource monitor. You can now close the task manger and only keep the resource monitor.
3. Click Network tab and hide everything except the TCP panel.
4. Start up Spiral Knights and sign up for a Coliseum Game (I only tested it for Lockdown by BN should be the same principle).
5. There should be two java TCP connections on the Resource Monitor. They should each have latency readings.
6. Keep an eye on those readings as you play your game and observe how they change.

SK mainly uses UDP for data, but TCP is sent periodically as checkups/overhead.

When you respawn in Lockdown, a TCP message is sent and the latency reading should always update. When someone kills you in Lockdown, and the kill cam starts, a TCP message is also sent. However, that TCP message comes from the server that the person you are spectating is playing on!
What this means is that you can get a reading for the round trip latency to the person you are spectating and compare it to your "normal" latency (ie.latency to your server).

I tested this theory in a Lockdown game and found that particular people consistently have much higher readings than normal.
For instance, my normal reading is 90-100.
When Player A kills me, it goes up to 145-149.
When Player B kills me, it goes up to 120-128.
When Player C kills me, it stays in 90-100.

There was no incident where the latency dropped significantly in the kill cam. This makes sense because the server I'm playing on should be the one with the lowest latency to me.