Are there any special meaning or purpose to the colours used for other world encounters, or are they just picked randomly?

For instance, do the blue bordered cards have a higher chance of something beneficial happening and the red bordered cards having a higher chance of something bad?

Also, is it more dangerous to travel to some other worlds than others, or are they all pretty much on the same level?

Kevin explained what the colors meant last summer

http://www.fantasyflightgames.com/edge_foros_discusion.asp?efid=5&efcid=1&efidt=135388

Very enlightening. So it seems that some OWs are definitely more dangerous than others (which makes sense), although none of them are exactly "safe" (which also makes sense.)