How to change the color of console error messages?
I assume something has to go into "preferences.txt"? But what?
It's not in preferences.txt, but in the Arduino IDE's theme files. I have documented the theme settings, as well as provided a dummy library for testing custom themes here:
Please let me know if you have any problems or questions while modifying your theme.
One of the key things people who design web sites and human-computer interfaces need to know is that nearly 10% of the users will have some degree of color blindness. so things like green on red are particularly poor ideas. The default should always be to use intensity, not color first
Yes, it's definitely a problem. There was some discussion about fixing it here:
Sadly, the person requesting the change took the stance that the only acceptable fix was something that would significantly harm the usability of the Arduino IDE for the other 90% of the users, and refused any consideration of compromise. Then another user jumped in to add unproductive comments. That resulted in the discussion breaking down and no resolution was ever reached. It's a real shame, because there was some good momentum to implement a fix.