Answered my own question. Missed it the first time I searched.
Documentation » Features » Session URL will give the answer to handle special characters.
I'm automating a sftp upload to a 3rd party vendor site. They provided the username & password. The password has the ":" character in it. The script accepts the username then I get:
Authentication with pre-entered password.
I know the password is valid because I'll copy and paste it into the winscp.exe and it will work with no issues.
Is there an issue with using the ":" character in the script such as: