Footnote reference appearance in compiled document

I have been testing the footnote functionality for Kindle publishing and I’ve been able to successfully publish linked footnotes to my device. However the inline footnote reference is almost invisible on the kindle. It is quite small and is not black but rather appears like a light grey. It will be important for the footnote reference to be black and visible as my project will rely heavily on cited material.

How can I modify the final appearance of the footnote reference in the compiled document?