Which combining form refers to a color associated with oxygen deficiency?

The combining form "Cyan/o" refers specifically to the color blue, which is commonly associated with oxygen deficiency in the body. This condition, known as cyanosis, occurs when there is a lack of sufficient oxygen in the blood, leading to a bluish tint, especially noticeable in the skin and mucous membranes.

The other options refer to different colors: "Erythr/o" pertains to the color red, often associated with red blood cells or conditions indicating increased red cell levels; "Eosin/o" is related to a rose or pink color, typically connected to eosinophils in the bloodstream; and "Dermat/o" refers to skin, not a color at all.

Thus, "Cyan/o" is the only combining form that accurately links to a color indicative of oxygen deficiency, making it the correct choice.