You could do something like this:
alias: Office Brightness
description: Set brightness on Smart bulbs when Switch is updated
trigger:
- platform: state
entity_id: light.office_light
condition: []
action:
- service: light.turn_on
target:
entity_id:
- light.office_rgb1
- light.office_rgb2
data:
brightness: >-
{% if state_attr('light.office_light', 'brightness')
%}{{state_attr('light.office_light', 'brightness') }}{% else %}0{% endif
%}
mode: single