If you want to go with the Phillips Hue option which allows you to change the colour temperature of each downlight; here is what you need to consider:
We will need to replace the existing downlights for the Phillips hue downlights, they are bigger (the 125mm round size ) than a standard downlight which is usually 90mm. The cost per new unit is around $60AUD and the replacement of the old for the new one will be $40AUD each; a total of $100AUD per downlight you would like to replace.
Things to consider with Phillips Hue:
There is no manual override (you need to leave the light switch at the wall on the ON position at all times, the controls happen over the app on your phone only).
The amount of lights, bulbs is limited to 50 per Hue Bridge/Hub, once the 50 is reached we will need to add a second bridge. There is another option which would be to go to a Z-wave automation system. We generally use a Fibaro HC2 controller:
This system allows us to do a few more things and it works differently than the Hue. It allows you to control all the existing light fittings at home by installing an ON and OFF module behind each light switch you want to control, we also have dimmable modules for the dimmable lights. The investment for this system will be a bit higher as the Hub main controller gateway is $1200AUD and the cost per smart switch installed is around $299AUD each.
Things to consider with Z Wave:
There is manual override; the normal light switch on the wall will remain as it is and will function turning the light on and off as well as from the app on the smartphone and/or tablet.
It has the option of adding voice control.
The amount of modules per controller is 259.
It is the entry point to a more scalable system that will allow you to bring in more things like Motion Sensors, Door/Window Sensors, Sensor Gate Motors, Intercoms, smart locks etc. as you get used to automation.