How to use the gem detector in Luigi's Mansion 3

The Gem Detector detects where undiscovered gems are hidden. In the old water storage yard after taking Tonobio to open a new road, there is a suspicious mark on the wall in the upper left corner. Use a paint bucket to hit it and drain out the mark. The gem ghost will appear and you can get it after destroying it. "Luigi's Mansion 3" is an action-adventure game for Nintendo Switch developed by Next Level Games. It is the third game in the "Luigi's Mansion" series. The game was first announced at the Nintendo Direct held on September 14, 2018, and was released globally on October 31, 2019.