What does the Red and Yellow colored messages denote while saving/publishing elements/activities or while uploading a CSV file?

Red message: You’ll see a red colored pop up message while trying to save or publish your element or activities or while uploading a CSV file when the system notices that there is an error in your data or if anything has been done incorrectly. The system will not allow you to move onto the next step until you make the required corrections. 

Yellow message: If you see a yellow-colored pop up message, there are some improvements you need to make to your data. Specifications will be provided in the message itself.