transmission fluid that indicate must change

[susucosp]

can anyone tell me what color and smell of the transmission fluid that will require change. if it does not need to be change, that is the best. i check the stick of the transmission oil with a white tissue paper, the color look like brownish when wet but when dry on the white tissue paper, it look like purple in color. i try to smell, and cannot smell nothing burn smell. so, do i need to change the transmission fluid at all?

my car is reach 100K miles, front disk brake never need change, it is still like new. i only change the rear drum brake of my car, of course, i have to change oil, and filter, air filter, battery, tire, make tire rotate, wind shield wiper, spark plug, ...