Colour glitch in bqm?

I have a BQM snapshot with a light blue spike on it:
weird colour (cyan?) (about midnight). I've never seen that colour before. I guess it is a big spike in average latency.

It worries me there's quite a few "red spikes" of dropped packets, which generally coincide with a largish download or speedtest. I can't see anything in mydslwebstats that shows a line problem; if that's true, can I infer that the packets must be dropped somewhere beyond my exchange, maybe in plusnet-/bt-land?

Click image so its larger you can see its blue line with green/yellow next to it

If spikes coincide with traffic then nothing to worry about overall I'd not blink an eye if that was my BQM

I'm with Plusnet and saw a similar spike (my bqm) and am not alone as this collection shows.

Was not the pingbox itself as can see other ISPs without the issue

Thanks MrS, another unexplained oddity in the Plusnet network then!