You can change links' colorings and formatting as it will send out. However if a recipient's device / email program is set to automatically convert all links to blue underlined text, and all clicked links to purple underlined text, then there's nothing to be done about that.
Email border color and thickness can be edited via the Design tab of the lefthand menu.
If the border you're referring to is for table cells within a CPE email, then you can edit that when formatting the table itself.
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