Grease manufacturers use colorants only to help identify the grease and make it more attractive, not just brown or black. Color can help users find incorrect grease. For example, when another color of grease is needed, a certain color of grease appears in the grease gun.
The color of grease can also provide some indication of its overall quality. As the grease degrades and becomes contaminated, it usually starts to darken. Compared with new grease, this darkening may be more pronounced, which may indicate that the grease has reached the end of life limit. Although the darkening of grease is not surprising, the speed at which it darkens is an important factor.
In addition to the darkening of the grease due to operating and environmental conditions, a change in color may indicate that the grease is inadvertently mixed with a different type of grease. If this happens, action should be taken immediately to determine how and why this happened. Carelessly lubricating with the wrong grease is more common than most people realize.
A quick solution is to use different types of joints for various types of grease, such as ordinary joints for independent bearings and button head joints for motor bearings. Another option is to leave a mass of grease on the grease joint to indicate the proper color. This should only be done if there is only one grease with that specific color in the facility. The type and color of grease should also be marked on the grease gun.
Remember that although the color of grease may provide quality information, it is only used as a brand to indicate the type of grease (usually by type of thickener). However, keep in mind that there is no guarantee that the grease color specifies a specific thickener type, even in the products of a single grease manufacturer.
The following table shows how a specific grease color refers to several different types of grease, especially lithium complex grease.