Hovis builds a garden office*

Hue is the answer - assuming you're running internet down there.

Ideal setup would be something like:

1. Run ethernet to the shed / office
   
2. Have an access point (google wifi etc) in the shed / office
   
3. Setup a hue bridge for the house
   
4. Install Hue bulbs on the outside / inside of shed / office
   
5. Control from app
   
   

This is what we did for our garden office in the last house as it was used as an office.