I haven't seen much interest in colorPicker for RF4 so far, either in JIRA  or Roadmap planning discussion .
What about alternatives?
I can see that PrimeFaces has colorPicker component ,
or you can surely contribute to the project and use RichFaces CDK to migrate RF3 component to RF4 .
Anyway, creating JIRA for providing colorPicker in RF4 is good idea !