Does the color of lubricating grease have any significance?

The color of unused lubricating grease can be natural (light tan to black, depending on the formulation), or colored with a dye.  Black greases typically contain molybdenum disulfide or graphite, both of which impart a dark gray to black color to the grease.  The natural color of most greases is light tan to medium brown.  Manufacturers add dyes to some greases to give them distinctive colors, either for marketing purposes or to make them easy to distinguish for maintenance personnel.