As the subject says, I want to change to something other than the very light grey as shown below (line 319). I have a hard time seeing that, especially when doing a 'find in files' command.
The easy way: Pick an alternative Color Scheme:
Preferences > Color Scheme > ...pick one
The more complicated way: Edit the current color scheme file:
Preferences > Browse Packages > Color Scheme - Default > ... edit the Color Scheme file you are using:
Looking at the structure of the XML, drill down into dict > settings > settings > dict >
Look for the key (or add it if it's missing): lineHighlight
. Add a string with an #RRGGBB
or #RRGGBBAA
format.