First thing you'll need to do is to determine your "theme", which I emphasized on my previous post entitled "My Wedding Preparations".
Now, that you already have decided your theme, you can now then choose your color, which should compliment the venue itself. For example, if you are having a garden wedding see this image below:
Or a church wedding?
or a beach wedding?
The color is unlimited, the choice is yours...Just use varying shades of one color accented with white or cream to create a very visual and striking combination.