i want SMTP email subject should be in red color
You can’t as the mail protocol doesn’t support formatting the subject line.Highlighting certain items is a function of the mail client being used at the receiving end and a choice of the receiver and not the sender.
Coloring a subject is not an E-mail or SMTP feature. It gives ability of client to show HTML documents. Clients that support HTML format parse email body only and show subject as-is. Therefore subject remains as it was created.
So, the bottom line: no you cannot send email with colored subject. I am sorry.