Color of Water

Without a human eye and brain there is no color!


Bryce Johnson, Lori Lambertson, Anna McGaraghan, Paul Doherty  

This workshop is available on the website :

The plan

Discussion question in small groups: 1. What causes the color of water? 2. Pick a color on the chart and guess why the water might be that color.

Look at the color of tap water in a long tube.

Exhibit: Colored Shadows, to show color subtraction (PD)

Make turbidity tubes, calibrate them using different dilutions of TSS. Graph data. (LL, BJ)

Make hinged mirrors.

Walk to St. Francis pier:
turbidity tubes (BJ, LL)
hinged mirrors (BJ, PD)
color charts (BJ, AM)

Phytoplankton and water color (AM)

Color dilution (BJ, LL)
Lee filter demonstration (PD)

Reflection, absorption, scattering (PD)


Colored shadows  Combine light from red, green and blue bulbs to make white light, then use shadows to subtract colors.

Disagreeing about color, This exhibit answers the question "Do other people see the same colors I see?"

Mix and Match  How many colors can you see?


CD Spectrometer Make your own spectrometer with a compact disk.

Turbidity Tube

Serial Dilution and Phytoplankton

Articles and Websites

Red and Black tides, pdf

Ocean Data Center

Ocean Color Web


Colors of Water

Colors of water

Turbidity tube calibration

Turbidity Tube Calibration

Turbidity Tube Calibration

Reflectance of Water versus angle

reflectance of water versus angle

Lower curve is light polarized perpendicular to the water surface, upper curve is light polarized parallel.

Red Tide (Wikimedia commons)

La Jolla Red Tide

Images from the article Red and black tides

Color of the sea versus biomass in mg/m^3

Color of the sea versus biomass

Absorption spectrum of water

Absorption Coefficient Spectrum of water


Water Absorption Ciefficient visible spectrum

The Absoption Coefficient, a m^-1 of pure water in the visible part of the spectrum.

I = I0 e^(-ax)

Absorption spectrum of chlorophyll

Chlorophyll absorption

The sensitivities of the human cones

Sensitivities of human cones

The CIE Color Chromaticity Diagram 1931

CIE Color Chromaticity Diagram

The official names for colors. The spectrum is wrapped around the upper boundary with wavelengths in micrometers.
If you mix two wavelengths of light, draw a line between the wavelengths, move along the line to mix colors and see the resulting color.


One yellow gel

Two yellow gels

Three Yellow Gels

Four Yellow Gels

Five Yellow Gels


Scientific Explorations by Paul Doherty

© 2011

July 2011