Automatic transmission fluid color, along with other symptoms, can be an indication of an automatic transmission problem. The color of the transmission fluid alone, is NOT a reliable indicator. Transmission fluid color varies widely with modern fluid. Darkening of fluid with age is also a normal characteristic. Knowing the normal color and looking for other symptoms can prevent being taken advantage of.
Several times a month, folks come in thinking they need automatic transmission repair. Sometimes repair is needed and many times it is not. Often, the reason they felt repair was needed is another shop told them the fluid was dark. Transmission flushes are very profitable and fluid color may be used as an excuse to sell the service.
New automatic transmission fluid will have a bright to dark red, translucent color. The red color is the result of dye that is added to the fluid for identification. It is NOT an indication of the quality of the fluid nor the condition. An automatic transmission can have a significant amount of wear and still have clean red fluid. It could also have dark fluid and still be in great condition.
Transmissions that have not been serviced, will benefit from a proper service. The color of the fluid alone is not an indication of the need for service. Many newer fluids are significantly darker than fluid of the past, even when new. Color ranging between the first and second illustration are typical for new fluid.
Even very dark fluid, with no other systems or indicators does not mean there is a problem. Fluid that has not been replaced for 100,000 miles will often be very dark. The automatic transmission may also still be in good condition.
Restriction of the automatic transmission filter is much more of a problem than dark fluid. This is another reason why automatic transmission flushes are ineffective. Replacing dark fluid and not the filter will not help. With very dark fluid, it may also take more than one service for the color to return to normal.