New transmission fluid is usually transparent, and relatively odourless. A few years ago, virtually every transmission fluid was red; technicians would aptly describe a transmission with exceptionally clean fluid as being “cherry.”
Today, many manufacturers have begun to stray from the traditional red colour. Transmission fluids may be green, yellow, some may even have a bluish tint. But in virtually every case, clean fluid will look clean, and smell clean. So checking the fluid’s colour and giving it a little sniff is a great way to determine whether your transmission is in good shape, or in need of service.
For further information please read this printable ATRA™ Consumer Bulletin.