"Cuiabá [River] joins the Paraguay River inside the Pantanal National Park, Pantanal, Brazil" -- Photo by Scott Warren -- Click through to learn of conservation efforts for the world's largest floodplain. Other photos of this confluence: http://www.macaulay.ac.uk/pantanal/images/cuiaba_river.html and http://nationalparkorgenglish.wordpress.com/
"Triple Frontier: The Tri-Border Between Argentina, Brazil and Paraguay" -- "...this in particular is formed naturally by the convergence of two rivers - the Paraná River and the Iguazu River." Click through to see the monuments in each country and the amazing Iguazu falls.
"Where the Rivers Collide: Park offers look at the confluence of Willamette, Columbia rivers -- Kelley Point Park [in Portland, OR] is the confluence of the Willamette and Columbia Rivers. / Thomas Patterson | Statesman Journal"
"Flooding at the confluence of two great rivers [the Mississippi and the Ohio at Cairo, Illinois]. Photo by John Blair Valley Watch [May 2, 2011]" -- Compare http://pinterest.com/pin/175218241723426989/ and http://pinterest.com/pin/175218241723427550/ for non-flooded photos.
"Easter Creek and Kilik River confluence -- Aerial of the Brooks Range mountains, arctic Alaska. Confluence of Easter Creek and Kilik River, Gates of the Arctic National Park." (With rainbow bonus!) Prints available at click-through; photo by Patrick J. Endres.
"Where Two Oceans meet" -- Conflict over where the Indian and Atlantic Oceans meet; officially, it's off Cape Agulhas, South Africa. Shown: "The RAF's Red Falcons jumped over Cape Agulhas - the small peninsula at the bottom of the photograph. The oceans don't respect any lines that are drawn by man..." Click through for more photos and explanations.
Not a confluence, but still unmixed color shown here in "Green is the colour: Landmarks lit up to celebrate St Patrick's Day " -- Shown: "America: Workers spread an orange powder to dye the Chicago River green before the start of St. Patrick's Day Parade"
"Confluence of...Rio Uruguay & tributary, Misiones province, Argentina. Drastically cleared to make way for farming, the tropical rainforest of Argentina is now in some areas a less effective defense against erosion than it was in the past. The heavy rains in the province...wash the soil & carry off significant quantities of iron-rich earth into...Rio Uruguay, turning the waters a dark, reddish colour...this sediment is dumped in the estuary of...Rio de la Plata..." More at click-through.