When pressing "Validate" button, the system will tell you if you have an invalid or incomplete data. 

Light yellow codes are useful notes that may help you improve the accuracy of the return. It is a notification/warning and you can still proceed and make your form VALID.

Light purple (or light red) means an ERROR, that you need to resolve in  order to proceed with validation and completing your forms. Click the necessary error that requires your attention and make a necessary changes. Keep doing this until there aren't any validation error code items left.