How to remove colored lines from left side of forwarded emails

I am an artist who keeps an email with my artwork to send to prospective clients. As I constantly add artwork to the email, a colored line appears on the left of the forwarded component of the email. I've tried deleting these lines, but they are not removable. Is there a way to keep an email, forward it to clients, and then add more info to it without the color coded text showing up each time? The more I send it, the more lines appear on the left of the content.
I think if I can't remove the lines, I will have to copy and paste each art piece separately into a new email, which is a lot more tedious. Unless someone can come up with an easier way to do it?

I hope my description isn't too confusing. Sometimes I can't figure out an easy way to explain computer events!