We found the culprit, thank you for helping us find it. Please quit, SketchUp, open /Applications/Utilities/Terminal.app, and type in or paste (whichever version you’re crashing in - 2017, for example):
defaults delete com.sketchup.SketchUp.2017 “NSWindow Frame NSColorPanel”
and hit Return. Then restart SketchUp. It should be noted: don’t drag Materials added by SketchUp to the Favorite Swatches panel at the bottom of the NSColorPanel, or this crash may happen again.