Apply custom styles to ngbtooltip in angular

I want to apply custom style to my tooltip as shown in image.

Please help me..
Thanks

you can change the style with the attribute tooltipClass and a style for the new class.

<button type="button" ngbTooltip="Upload new document" tooltipClass="my-custom-class">
  <img src="plus_button.jpg">
</button>

.my-custom-class .tooltip-inner {
   background-color: lightblue;
}

.my-custom-class .arrow::before {
   border-top-color: lightblue;
}