What is the main color change observed in the LMG test when blood is present?

In the LMG test, which stands for Leucomalachite Green test, the presence of blood is indicated by a dark green color change. This is due to the reaction between hemoglobin in the blood and the chemicals present in the LMG test, leading to the formation of a compound that exhibits this distinctive dark green hue.

The test is sensitive and can effectively identify blood at crime scenes, enhancing its utility for forensic investigations. The dark green color change is notable as it allows investigators to confirm the presence of blood even when the sample may not be visually apparent.

Other options, such as dark blue or bright red, do not accurately reflect the chemical reactions occurring with hemoglobin in this specific test, and light green does not signify the presence of blood in this context. The key takeaway is that the dark green coloration specifically signifies a positive identification of blood in the LMG test.