I've read some questions and answers on a few websites, including this one but it doesn't seem to answer what I'm looking for, which is:
What are (generally speaking) the best colors to show both messages of approval and error messages in a form?
I've read about some psychological reasons why using green for approving and red for an error seem to be the best, but I'd like to know if there are any studies or data on what color should be used to show these types or messages in forms.