First of all, welcome to the forums.
If you are a newcomer to the simulator it would be to your own benefit to also read through the FAQ. It's a sticky thread on the main page, it explains various things you might want to know and even offers some workarounds for bugs that are present in the simulator. We expect a lot of those issues to be cleared up with the upcoming patch, but for now it will save you the trouble of finding out and working around the bugs all by yourself.
As for your current issue:
Go into the options and select video.
Click on the "custom" tickbox to get the full range of available options.
There is another tickbox labeled "anti-epilepsy filter" which is on by default due to a legal requirement when you first install the simulator.
Disable the anti-epilepsy filter (unless you suffer from an epilepsy condition of course!) and your graphics should display normally.
I hope it helps, reply here in this thread if you need further assistance
