I need help with Firebase data changes

hello i need help
i am new in develloping projects
so i have a problem i need when a variable's data changed in my firebase data base
a thing( like marker's color) change in application

Please show your relevant blocks and a screenshot of your firebase data that shows the problem.

Also read this:

Having re-read your question, it seems you need to use the dataChanged event for firebase, targeting the tag of the variable you want to watch. When it changes use an if/else statement (if needed) to change the colour of the variable's marker (label?) in the app.