Trung999,
Are you sure you downloaded the latest madCAM release 2019-06-05 (21 MB) ?
I am also using the latest Rhino 6 update, but all versions since the madCAM 6 simulator fix have worked.
This is not crashing in the simulator with my most complex 4 axis simultaneous models.
I am running Windows 10 with the latest updates and ever since this release have had no issues.
Cut colour is located in the Layers Tab for example the toolpaths colours is the profile cut color, click the square to change it.
You can change colours on all activated items under the Layers tab, like your model colour.
Crashes in Rhino only occurred in the prior version of madCAM 6 (simulator issue) but not with the latest version of madCAM 6.
Regards,
Mauri.
ps. I did see you changed the cut colour in your crash picture.
Include your example in the next post so I can test the crash for you.