Built in datagrid tooltip css

Hi as you can see I have set Tooltip value to a text and a variable. How do I edit the css for the Tooltip. I tried to search for the class which controls the design on default.css page but had no luck.

Can you please help me out

This tooltip is the built-in browser one which displays when the title attribute of an HTML element is set. As far as I know it cannot be styled with CSS.