What is the different flavors? From the black, red, blue, and yellow packages.

Red - Red blend is recommended for those who love their espresso bold. This blend has a higher Robusta composition for dense aroma and body.Gold - Selected qualities of precious Arabica beans for a delicate taste and unmistakable aroma. Mild, smooth and refined. Less caffeine with tones of sugar, fruit and berries. Delicious as an after dinner coffee.Blue - For the coffee lover who enjoys the quality of Arabica but also a small intense note of extraordinary, this coffee has a smooth, refined flavor with hints of chocolate, perfect for the true coffee connoisseurs.Black - Blend of Blue & Red

can you use these pods with a senseo machine?

These are for machines that use the ESE pods. They are designed to be used under pressure with boiling water in an espresso machine, not in a drip coffee with hot water. I don't think they'll fit and I don't think the water will flow through as designed without the pressure.

Does this work on the Keuring Rivo Machine?

Caffe Borbone are ESE Pods, not K-Cups or anything made specifically for the Rivo. Here's a link to Keurig Rivo FAQs that definitively answers your question:http://www.keurig.com/mobile/customerservice/customerServiceDetail.aspx?itemID={BD1E694F-C9FD-4C72-BBF1-85F754C4358C}&sectionID=90a040bd-88af-4b3f-8ce7-a344c9f6b78e

Does it work with nexpresso

I think it wouldn't work with nexpresso, though I don't own one. I believe nexpresso works with a cup-kind of pod, this is just a little pillow, more like a tea-bag than a cup.