I changed the background color that is visible when hovering code (to black). For example when you hover over a method, you see its signature in a box; I mean the background col
If you want to change the colour of the hover over for a method that indicates you can click through to its declaration:
Preferences > General > Editors > Text Editors
There is a list of options in 'Appearance Color Options' in the right panel. Select the 'Hyperlink' option and change its colour.