Which factor does NOT affect the choice of coolants for nuclear reactors?

The choice of coolants in nuclear reactors is influenced by several key factors that affect their performance and safety. Corrosive properties are significant because a coolant must not react adversely with the materials of the reactor system, leading to degradation over time. Density is also important, as it affects the flow characteristics and heat transfer efficiency. Availability plays a critical role as well since a coolant needs to be sourced economically and consistently to ensure the reactor can operate effectively.

In contrast, color is not a relevant factor in selecting coolants for nuclear reactors. The color of a coolant does not impact its thermal or chemical properties, nor does it affect how it behaves under operational conditions. Therefore, it does not play a role in the functionality or safety aspects of the coolant in a nuclear system, making it the correct choice for the factor that does not influence coolant selection.