Signs are always easy communicators. It is more so with colours, as they carry their own connotations.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/colour-coding-can-help-understand-quality-ecosystem
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/times-india-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/ecosystems
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/national-biodiversity-authority-nba
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/biosafety
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/chilka
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/biodiversity
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/environment