This idea comes from Los Altos UMC in Long Beach, California, USA.
A group of us met, gathered supples and painted six doors the individual colors of the rainbow. Our church resonated with (and remembers well ...) the UMC "Open Hearts, Open Minds, Open Doors" campaign ... so we painted that onto the doors. These doors have become a prophetic witness on our campus in different seasons.
One Sunday, we actually processed the doors in ... one by one ...during the Introit, placing them in a row across the chancel. It was incredibly powerful for the church and that service. Additionally, having the doors outside has been a powerful statement for the church and our local community.
We also recently purchased large rainbow flags that fly on a well-trafficked corner of our campus.