Startup Idea : Paint changing colour based on environment changes

This paint can be good for safety purposes especially in Workshop environments. Maybe u just paint a section of an area every few meters. Now maybe a dangerous chemical is leaked into the environment a few 100 meters ahead. As you are nearing the area not yet in danger you see ahead that a section you painted has turned a dark blue. Your life is saved; you can activate the alarm ; clear the building preventing any accidents. It's just an idea. Maybe red can be used for fire warnings.