In this site you will see several times these two red and green symbols placed in correspondence with the fields that the user can fill out. Following their meaning:
The red color indicates a field not filled in or a field filled in incorrectly. If the color remains red (on at least one of the fields) it will not be possible to continue with the operation.
The green color indicates the exact compilation of a field.
The "X" present in the text fields allows the content of the field itself to be emptied.