According to Elizabeth Stewart Clark, these were “originally shot by Kathleen Lowe, of Utah; she and her husband … both did wet-plate work, and this color wheel study was done for their website,” which has since been taken down.
On May 8, 2004, I received official permission and encouragement from Mrs. Lowe to store these here. (Thank you!)

The Color Wheel.

The Same Wheel, in Modern Grayscale.

A Wet-Plate Collodion Image of the Same Wheel.

Wet-Plate, Original, and Modern Grayscale.
Note how dark “warm” colors tend to turn in period photography, and how light “cool” colors look. Even a very dark blue could look much lighter to our modern eye, while yellow could look dark, and orange look black!
Also graciously added by Ron Myzie: “As you know, when white light is passed through a prism it breaks down into a spectrum (rainbow). Early photographic materials were sensitive to the blue wavelengths of light only, and were more or less blind to the rest of the colours. This is why anything that is blue appears light while other colours tend to be darker in early photos. Common modern black and white film is ‘panchromatic’ — sensitive to all colours…”
“Now, if you’d like to try to convey some of the appearance of early photos with modern black and white emulsions, place a blue filter over your lens when you shoot. The film will respond to the extra blue by lightening blue objects and darkening other colours — rather like early films.”