docker build -t hello-docker-web:<your tag> .
To run the app with the default background color (default BG_COLOR = blue):
docker run -p 3080:3080 -e BG_COLOR=red hello-docker-web
To pass a different background color as an ENVIRONMENT variable:
(acceptable BG_COLOR values: black, white, red, yellow, orange, pink, blue, grey)
docker run -p 3080:3080 -e BG_COLOR=red hello-docker-web