You may have already come across this, but the source for a version of a DaisyLink multicolor LED is available on codeplex ([url]http://gadgeteer.codeplex.com/SourceControl/BrowseLatest[/url]), under the Modules/MSR/MulticolorLED directory. The design is different from the GHI version, but implements very similar functionality.
The chip it uses is a Cypress PSoC. It is an interesting chip - an 8-bit MCU with some programmable digital/analog ‘blocks,’ which can be configured to provide different interfaces and capabilities, and ‘connected’ to any physical pin. For example, you can drag a ‘UART’ module into your design, and configure it to connect the TX line to pin 3, and the RX line to pin 4. It’s a bit like an easy-to-use FPGA, with many ready-to-use modules. We have often found it useful as a general-purpose prototyping chip because of its flexibility. The programmer is also relatively inexpensive (about 28 dollars from Digikey, part number 428-2021-ND).
Even if you don’t use this particular chip, the source code for the firmware should be useful. It is written in C, and should be a good guide for porting to another platform.