Your comment makes me think of LabVIEW - if you're not familiar with it, it uses a visual programming language ("G") in which data flows down wires. The color of the wire indicates the wire's data type (blue for ints, orange for floats, green for bools, pink for strings) and the width of the wire indicates the dimensionality of the data (thin line = scalar, thick line = 1D array, double-thick = 2D array). The color is more than decorative or even assistive - it's essential to understanding the program.

> The reason traffic lights are colored is because they are showing distinct states of the same thing and the color is the means of differentiating

I wonder if traffic lights were invented today, would it be just one light changing colour?

That does exist, it's called semantic highlighting.

In any case, my analogy was not perfect, but neither was Russ's! The point is it's totally normal and not "childish" to use colours to help distinguish things. Traffic lights do not technically need colours (you can use the position of the lights - I assume that's what badly colourblind people do). Nor do transit maps technically need colours - you could just label the lines, or use patterns.

https://www.flickr.com/photos/gywst/1407078279

It's completely absurd to say that colours are childish because they can help children.

There are a bunch of identical things on my screen called lines. They contain a bunch of mostly identical things called tokens. Syntax highlighting uses different colors to identify the different purposes of all of these tokens blasted onto my screen.