After upgrading to OS X 10.9, I found that whenever I copy/pasted text from a terminal window to TextEdit or an email message, it would paste using the same colors/background as was in the terminal. In my case, this meant that the text was white on a gray background. This was annoying, since I just wanted to see the text. To fix this, enter the following into a terminal.

defaults write com.apple.Terminal CopyAttributesProfile com.apple.Terminal.no-attributes

It still uses the font from the terminal, but at least the colors are right.