Arrows on green tooltips are black

This issue is a port of https://github.com/scratchfoundation/scratch-gui/issues/9766

Green bubble tooltips like "Choose a sprite" have black arrows. This looks like a visual bug.

![A screenshot of a green tooltip with a black arrow](https://github.com/user-attachments/assets/0b42c6e0-8ae9-4856-9a91-7403100f14a4)