I had pasted a chunk of text from an online text editor into Scrivener. Then I tried to change the font color of the chapter. I highlighted the text, clicked the font color button and it stopped responding.
For some reason, it saved the file weirdly too. When I reopened the file, it had apparently saved the text but lost all formatting. I never saved the file either.
How long was the section of text you highlighted? If it is very very long, slowdowns might happen and the program may not look like it is responding as the .rtf editor isn’t handling large documents very well.
I haven’t yet been able to make the program crash with just changing the colour of a few lines of text.
Edit: Yep: The .rtf editor hates large files. 
It was 1545 words and 8090 characters
Thanks for the feedback, I’ll try to duplicate this with a large selection of text.
Lee
This has been fixed in Beta 1.2.
See http://literatureandlatte.com/forum/viewtopic.php?f=32&t=9100