To offer the i-Brix systems we're making available to Kickstarter backers, the base (32 x 32) will be available initially in one color. The color will likely be grey (ie, similar to LEGO® grey).
In order to effectively keep track of orders and fulfillment when we go to ship product, the assorted color brick sets will not be configurable - for example, we will not be able to address each order to provide all red bricks only, or all blue, etc - or, 1/2 blue, 1/2 red, etc.
However, if you elect to increase your pledge to cover more than one set, you could opt to have all white LEDs in one kit and the assortment of colors in the other.
In the future, we do plan on offering add-on bricks in different colors (that you can choose)