Final answer:
The rates of fire represented by the 3-second green flame and 4-second yellow flame seem to discuss rocket engines rather than firearm rates of use by the NMCB, likely indicating different stages of rocket thrust using liquid and solid fuel mixtures.
Step-by-step explanation:
The three rates of fire mentioned in the question, and referenced by the 3 s (green flame) and 4 s (yellow flame), seem to describe different engine thrust profiles rather than rates of firearm use by the Naval Mobile Construction Battalion (NMCB), which could be a possible misinterpretation of the original question. Typically, the NMCB might use terms such as sustained, rapid, or cyclic when discussing weapon fire rates. However, the information provided seems to refer to rocket propulsion, where a liquid fuel/oxidant mixture might be used for one phase of the fire, while a solid mixture is used for a more powerful, subsequent phase.
In the context of rocket engines, the 3-second green flame indicating the use of a liquid fuel/oxidant mixture could represent a different rate or stage of thrust compared to the 4-second yellow flame, which indicates a solid fuel mixture possibly representing a stronger thrust stage. However, if the question was intended to be about firearms, this information wouldn't align and could imply a misunderstanding. In general, firearm rates of fire are categorized differently and not by the color or duration of flame.