If red is the color of caution/ alert, why is it used in some email address background?

I’m not where sure you got your premise that red is the color of caution/alert. In traffic signals yellow indicates caution and red means stop. In any case, colors can be used in multiple ways, not just one.

Your example explains that it turns red because it is an incorrect email address.

@chyna The link I posted says not.

By the way it happens the first time only according to my experience.

@flo That’s what I get for not reading all the way down.

Red is certainly a widely used color on emergency vehicles and in emergency lights, and that’s all about caution and alert! It’s a primary color, and that’s probably also got something to do with it.

Different Colors can have different meanings in various settings. In your example also it’s indicating that you should “Stop” the action of sending the mail and check once more since the address is either incorrect or not in your contacts at the moment.

Is it interesting or what.

Thank you.