In the Sudan III test, what indicates a positive result?

In the Sudan III test, a positive result is indicated by an intense color, typically a reddish-orange hue. This test is specifically designed to detect the presence of lipids in a sample. Sudan III is a fat-soluble dye that binds to lipids, and when lipids are present, they absorb the dye, resulting in a noticeable and vivid coloration. The intensity of this color change directly correlates with the concentration of lipids present in the sample.

Other choices do not represent a positive result. No change would indicate a lack of lipids, while yellow or green colors are not characteristic of a positive lipid test with Sudan III. Understanding the significance of the intense color in this context helps to clarify the biochemical basis for detecting lipid content in various biological samples.