A mineral has a range of properties that define it. It can be thee density, the color, the streaks, luster and hardness. The chemical properties of the mineral are the certain indicators of its identity. However, the color is the most inconsistent feature. Hence, you cannot rely on color alone to classify different minerals. The same mineral can have different colors due to its composition.
A small difference can result in a major color change which makes it an inconsistent feature to identify or classify minerals. Yes, there is a standard color that relates with most minerals, but it is the shade that the mineral is found in usually, but there can be differences.