With the Pro version you have a lot of options to customize the tooltip. Below is an example of a tooltip with darker background and a white font color.

You’ll find all the options in the Tooltip section of your map. One of the important things is to set a maximum width for the tooltip, to make sure it doesn’t extend too much. Then explore the other available options to customize the visuals and make the tooltip the way you want.

The tooltip content is wrapped with the class .imapsInnerTooltip

You can also target the tooltip container using the css selector .map_wrapper foreignObject div