I'm using a theme, but I can't find the settings of this message which is almost unreadable. In the User Preferences / Theme / Info-tab are only a few colors to configure. I also searched in the User Interface settings for something like 'Error Message', but I couldn't find anything. Is there any way to change the color of this GUI component?
To my knowledge it cannot be changed, it is defined by the Box group in the User Interface tab. The only bits of it I could change were the border color and the gradient. The text color is changed globally it seems.
One workaround you could use is to tick the shaded check box and set both values to 100, this gives a bright white which might help against a darker color.