After you open your Start (Seed) Part, try opening the Appearance Editor (View, Color and Appearance), select your desired color, Part (which may be the default), Apply, and Close.
You can do this with an empty part.
Save the part. The next time you open the part your color appearance should...
I'm jumping in a little late here but there is a config option you can set that may help the performance. I opened a call with PTC recently and below is the response from tech support (I tried option one - setting the config graphics option to win32_gdi - and saw a huge performance improvement)...
