I have released a new version of this plugin that is compatible with the new plugin architecture. It is not backwards compatible; if you require compatibility with an older release of Kaleidoscope I suggest you stick with the previous release.
The new version adds user configurable options for the highlight color and shift key highlighting, documented in its README. It also attempts to use the hardware LED_CAPS_LOCK state if it can determine that this state is reliable (on my system it is not).
If you encounter any problems please let me know.