Why are indicators not used/required in some redox titrations?

[soccerboi]

^

[DisaFear]

Depends on what you use. Some of the chemicals you use will have colour changes of their own when reacting. I think KMnO4 has this

[soccerboi]

Yeh im using potassium permanganate. Could i say it is because of a change in oxidation numbers, resulting in a change in the colour of the solution?

[DisaFear]

This is what Yahoo answers says 

Some redox reactions involve transition metals which are usually colored, and so the colors of the metal ions in solution will do the indicating. But other redox reactions don't involve transition metals, and these require an indicator. For instance, when iodine is formed (as I3^-) in a redox reaction, starch is used as an indicator because iodine and starch form a dark blue complex.

What is true is that you usually don't use a typical acid/base indicator, but there are more indicators than the usual acid/base indicators.

[bob1234]

For the first time I would say Yahoo has pretty much got it spot on! Oh and remember that oxidation numbers don't represent any  physical quantity in fact its somewhat of an abstract idea used to determine whether a reaction is a redox reaction. 

[pi]

Note that not all redox reactions change colours, and there are "redox indicators" that change colour at specific electrode potentials

(you probably won' see any in VCE though)