There is no way to change link color for links in a headline.
Studio | Campaigns | Compose
Link formatting cannot be applied to headline blocks. Link color set in either global styles or selected block is ignored. The headline-only block doesn’t have the option to specify link font color.
It may be possible to set text color before formatting the text as a link.
- Highlight the headline text.
- Select a text color.
- Add your link to the highlighted text.
It is always recommended that a test email is sent before publishing to confirm that text formatting renders correctly in your chosen email client.
Please check the current status of this issue on the Known Issues Tracker. (Issue ID: PUB-1865)