I'm considering getting a Hubitat Elevation C8 but I'm not sure if it can do what I want. I can see I can set light colour temperature using rules, but is it possible for me to garauntee the temperature state after a light is turned on at the wall switch if it was off?
For example most rules that fire at say 6pm to set evening temperature, if the light was powered on at 7pm it would miss the automation and require a manual rerun of the automation. This is my issue with other simpler hubs I am trying to get around.
You can certainly trigger an automation (one of several available) from the light being turned on, and that automation could set the color temperature based on time of day. Generally, this might mean that the light first comes on to whatever it was set to before, and then changes to the desired color temperature a fraction of a second later.
A couple options here. Room Lighting, albeit complex, has an option to apply settings only to the light that turned on, meaning you could configure all the devices and their settings through it.
I have an app, Virtual Prestaging, which allows you to specify a primary (typically virtual) device; when any of the secondary devices get turned on, the color temperature gets applied in response to the on event.
Both of those, as Bruce mentioned, will typically have a flash of the old CT and then transition to the new one. The final option is to retrieve the desired CT and apply that as the action to take when the "on" button is pushed. That doesn't have the turnaround time of responding to an event, but may still transition through the old color.
Of course, all of these assume you have smart bulbs and switches which act as scene controllers.