It may be to do with the setup on the phone! I have iPad iPhone Android on a Moto g
All of them are blue on 'my stuff' and black everywhere else. The blue is darker on the iPad and if contrast is set wrongly on the other devices it will pale into insignificance!
Just to confirm, I haven't changed anything on any device and it's the same on tablet and phone and only since the other day (day before I posted I think)
I can confirm that we haven't changed anything at our end regarding this. I've had a closer look and there's nothing I can see that could be causing this. Maybe have a look at your browser settings?