Which factor is NOT critical when tightening hydraulic fittings?

The color and style of the fittings do not play a role in the mechanical performance or integrity of the hydraulic system when tightening fittings. Instead, the focus should be on aspects that directly impact the function and safety of the assembly, such as using the correct tools, adhering to manufacturer specifications, and ensuring that fittings are snugly secured without the risk of over-tightening.

The use of a proper torque wrench is essential because it provides the specific torque values required to properly tighten the fittings without damaging them. Following the manufacturer’s specifications ensures that the correct procedures and torque settings are employed, which is crucial for maintaining the hydraulic system's integrity and preventing leaks. Ensuring a snug fit without over-tightening is vital to avoid damaging the fittings or creating unnecessary stress that could lead to failure. Thus, all the other factors directly contribute to the reliability and safety of hydraulic fittings.