Throughout the GUI a simple colour coding is used to indicate: user input, information, or warning messages. ``Active'' regions such as buttons and region for inputting text have a yellow background with blue writing. (Note: the image of the data and the whole graphics window may be ``active'' for certain operations, but these are left in their normal colours.) General information text has a white background and black text, and warning or error messages have a red border and within black writing on a white background.
When warning or error messages occur there will usually be extra information in the terminal window, and other useful information can appear, so keep the terminal window visible at all times.