After blue, its now black. The colour of the water of river Dikhow has turned blackish these days.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/sivasagar-district-administration-test-water-dikhow
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/sentinel-guwahati
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/assam
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/sibsagar-d
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/dikhow
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/river-pollution
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/scientists
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/state-pollution-control-board-spcb-0
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-pollution