Looks like there are now 23 colors of MakerBot Filament. They have just added the following colors, which are available for purchase as of today:
True Green
Neon Green
Neon Pink
Neon Orange
Sparkly Dark Blue
Sparkly Dark Black
Here are some photos (the best I could find)
http://makerbot-blog.s3.amazonaws.co...ent_header.jpg