Colour Blocking is merely the use of blocks, of coloured paper, photos, journaling, etc. You can purchase templates for this technique and it's a quick way to make pages. But also for cards. This is a very simple card with 6 blocks of patterned paper in a grid design with a larger centrepice carrying a peel off and some embellishments. Simple but effective.
Here is an article about Colour Blocking at Scrapbooking.com magazine.
Here is a link to Papermaze - it shows you some of the templates you can buy to help you create pages usin this technique. And... you can turn each template through 90 degrees to make 4 different layouts, and then of course you can flip the whole thing over and have another 4!
If you want more information on this technique, search under "colour blocking templates scrapbooking".