Pebble isn't wasting any time. After shattering Kickstarter with the announcement of the coloured Pebble Time, the company just released their developer Software Development Kit (SDK). Pebble says that it will be easy to make existing apps work with the Pebble Time.
With our SDK, developers can start designing and building new color apps for Pebble Time, or upgrade their current Pebble apps to support Pebble Time. The SDK now includes an entire emulator (on cloudpebble.net or on your local machine) so you can get started on your apps before you get your Pebble Time. Documentation for timeline APIs is available as well.
More information can be found in the developer blog post: pbl.io/update3 or dive right in at developer.getpebble.com.