I tried to see if the selection background color or content assist popup can be changed to make it more visible in dark themes. Specifically on windows the selection background color is barely visible. I have some suggestions in this issue https://bugs.eclipse.org/bugs/show_bug.cgi?id=574412
please provide your feedback and suggestions as well. So i can try to provide a fix for windows to start with and then move to Mac. Not sure this is an issue in linux.
I would like if the theme can control the selection background color which will really benefit dark themes.