Thanks for posting in the Community forum.
We currently have no option to turn on the lights in random colors in the Routines. It's because specific actions are needed for the routines to work seamlessly. You need to indicate what color your lights will turn into for it to work. We appreciate your interest in this feature and we recommend you send feedback using your Google Home devices or Google Home app.
If you have other questions or concerns, feel free to let me know; otherwise, I'll be locking this thread in the next 24 hours.