Final answer:
In methemoglobinemia, blue skin coloration (cyanosis) is observed due to the accumulation of methemoglobin, which is incapable of binding oxygen, impairing the oxygenation of blood and leading to the blue appearance of the skin.
Step-by-step explanation:
The skin color alteration observed in a client diagnosed with methemoglobinemia is blue. This condition arises when the iron in hemoglobin within red blood cells (RBC) changes from its ferrous (Fe²⁺) form to ferric (Fe³⁺), forming methemoglobin, which is incapable of binding oxygen. As methemoglobin accumulates in the blood, it imparts a dark brown color to the red blood cells. As the percent of methemoglobin increases, the skin can appear blue, a manifestation known as cyanosis. Symptoms such as blue skin, labored breathing (dyspnoea), and possible confusion are indicative of increased methemoglobin levels. Methemoglobinemia is commonly caused by exposure to certain drugs and chemicals, which can increase the conversion of hemoglobin to methemoglobin.