Which test cannot be used to assess color vision?

The Fly test is not utilized for assessing color vision because it primarily evaluates the function of the visual system in response to motion and temporal contrasts rather than color perception. This test does not systematically measure how well an individual can distinguish between different colors, which is the primary purpose of the other tests listed.

In contrast, the pseudoisochromatic plates, Harty-Rand-Ritter plates, and Nagel anomaloscope are specifically designed for color vision assessment. The pseudoisochromatic plates consist of colored dots that form numbers or shapes to test color discrimination; the Harty-Rand-Ritter plates use a similar concept but focus on different color combinations to determine deficiencies; and the Nagel anomaloscope offers a more quantitative approach by allowing individuals to match colors and diagnose specific types of color vision defects. Hence, the other choices are valid methods for evaluating color vision, making the Fly test the outlier in this context.