is it possible to change the background color for tooltip? sure it is possible, more it is very easy.
you need to change color definition in file templates/wz_tooltip.inc.tpl on line 4:
[geshifilter-code language="javascript"]
ttBgColor = '#FFFFCC';
[/geshifilter-code]
as example you can make white background:
[geshifilter-code language="javascript"]
ttBgColor = '#FFF';
[/geshifilter-code]