The color of grease that is best will depend on the application for the grease.
Although red grease is often best for general purpose applications and offers good water resistance and moderate temperature tolerance.
Gray or black grease often contains moly or molybdenum disulfide and is suitable and best for severe conditions such as high loads, dusty environments and shock loads.
White grease or undyed grease is best for food grade applications and on machinery which processes or packages food.
Blue grease is best for high temperature applications or marine applications.
Grease can also darken in color over time due to oxidation, thermal degradation or even contamination, which can also indicate a potential issue.
The different colors of grease mean identification of the grease.
Grease comes in different colors mainly to be used as a visual aid and indicator for what the grease is used for.
For example some grease comes in colors like red for high temperature use and blue grease for wet conditions.
The grease color though is not a reliable indicator of the greases overall performance or suitability for any specific application.
The manufacturers use color in grease to differentiate the grease types, which makes it easier for you to identify the correct grease for a certain application.
The color of the grease can also help you quickly identify the different types of grease, especially when you're dealing with multiple grease points or routine maintenance.
The color of the grease does not guarantee the performance of the grease, like it's load carrying capacity , oxidation stability or water resistance.
The grease color can also change over time due to factors such as thermal degradation, oxidation or even contamination, which can indicate a change in the quality of the grease.
Blue grease is often associated with general purpose, water resistant greases, suitable for wet environments, like marine or wheel bearing applications.
Yellow grease can indicate biodegradable greases for use in light machinery or agricultural applications.
Green grease can signify the grease has environmentally friendly formulations or heavy duty uses and sometimes with added synthetic oils or additives used for resistance to oxidation and corrosion.
Red grease is often used for high temperature or heavy duty applications, although red grease can also be used for other purposes.
White or undyed grease is often used in food grade applications or machinery in which incidental contact with food is possible.
And gray or black grease can indicate that the grease has molybdenum disulfide or moly graphite that enhances wear resistance in severe conditions.