If the issue persist even on default theme, this means it is not because of X theme.
I did try again. For example this page: https://www.twoscotsabroad.com/how-to-save-money/
On that page I clicked this link
<a href="https://cabinzero.refersion.com/c/fe592" rel="nofollow" style="outline: none;">the Cabin Zero</a>
When I go back the link is still blue. Yes, when I click, and while still processing the link, it goes black. To avoid that, try this CSS:
color: rgb(51,102,255) !important;
Hope this helps.