Update Dec. 2018: as mentioned in howlger's answer, Eclipse Oxygen 4.7 (June 2017) does now include a way to configure the background color in popups: See "Colors in interactive popups" Interactive popups like JDT's Quick Outline don't use the platform's tooltip colors any more, since those were sometimes hard to read. Old style: New style: Go to Window > Preferences: General > Appearance > Colors
![Eclipse, change popup text background color when hovering the mouse on a keyword](https://cdn-ak-scissors.b.st-hatena.com/image/square/98d6f053a97a87156775f60757c60865d0f2c47d/height=288;version=1;width=512/https%3A%2F%2Fcdn.sstatic.net%2FSites%2Fstackoverflow%2FImg%2Fapple-touch-icon%402.png%3Fv%3D73d79a89bded)