The great river gets bluer

In Florida the Caloosahatchee River runs from the Lake Okeechobee to the Gulf of Mexico.  It crosses through several counties, including Lee County, dividing it roughly in half on a diagonal.  There are several river crossings in Lee County, including the Alva bridge, Rt 31 bridge, the railroad crossing, I-75, the Edison Bridge (now a pair of spans), the Caloosahatchee Bridge, the Midpoint Bridge, the Cape Coral Parkway/College Parkway bridge, the Causeway to Sanibel, and, the causeway to Fort Myers Beach.

Since I drive around so much, I have the opportunity to see the Caloosahatchee River at different times of the day, every day.

When the temperature gets cooler, the water looks bluer.  I want to know if it just looks bluer to me, or if the water changes by getting cooler, and thus changes color. Does cooler water look darker, or is it actually darker?