Final answer:
A medical assistant would use the Ishihara color plates to assess color vision. This test involves identifying numbers within a circle of colored dots to evaluate color perception.
Step-by-step explanation:
The tool that a medical assistant (MA) would use to assess a patient's color vision is the Ishihara color plates. The Ishihara test evaluates color perception by assessing whether individuals can discern numbers that appear in a circle of dots of varying colors and sizes. The Snellen chart is used for testing visual acuity and not color vision. An otoscope is used for examining the ear, and an ophthalmoscope for examining the inside of the eye.