What does transformer oil colour indicate about its condition?

The color of transformer oil is a key indicator of its condition. Typically, clear or light yellow oil signifies good quality, while darker shades, especially brown or black, suggest the presence of contaminants or degradation products. A dark color may indicate oxidation, thermal degradation, or the presence of moisture. Regular color assessment, along with other tests, helps in monitoring the health of the transformer and determining the need for maintenance or replacement of the oil.