This review is from: Colour Index (Turtleback)
This handily sized guide is great as an inspiration for that next colour scheme that you need. Organised into 2,3 and 4 colour groups it gives you instant ideas for print or web. Colours and their combinations are also grouped into collections like 'active', 'quiet', 'progressive' etc which again is a useful touch.
It's worth noting that each colour is listed with its CMYK and RGB references - just plug them straight into your design program.