On the other hand, my medics do email, which is nice compared with the UK.

@pseudomonas those replies are indeed annoying. "We couldn't get through to you please call us" is another tedious variant I get quite often.

blue means iMessage on iPhone. So it indicates the person is an apple user. Don't know how that means anything.

@GreenSkyOverMe means they're both using the Messages app on an apple device (iphone, ipad, mac). secondarily, that they can confidently send other media eg: photos, videos to each other; it doesn't depend on phone networks to work (once each end knows the other is on iMessage, it just goes over internet) and is secure (end-to-end encrypted)