The color of transmission fluid can indicate the state of the transmission. New transmission fluid is typically bright red in color and translucent. As the fluid ages, it can turn into a light brown color, which means that the fluid is getting older. A bad transmission fluid color is muddy brown, dark brown, or black, which can indicate that the transmission needs maintenance. A bright and deeper red color is normal, while a brown or burnt color are good indicators that you need to arrange a transmission fluid change or flush. In summary, the color of transmission fluid can range from bright red to light brown, and a bad color can indicate that the transmission needs maintenance.