Very sorry about this and not sure how it’s happened even, but it’s actually a Reboot problem. I will open up a ticket to get this fixed in the next version.
In the meantime you can make the change yourself easily enough, and make it to Reboot itself not a child theme (unless you are running a child overlay in which case you will need to make the change there).
Open Minimal overlay – sp-resources > forum-themes > reboot > styles > overlays > minimal.php
Locate $postLinkColor on line 357.
Change value from $baseColor2 to $baseColor6.
Should fix things up OK!