Aux cable with red, white and yellow sheild colors

[matthex0]

After stripping an aux jack I have found a red, white, and yellow shielded wire inside. I am wondering which one is right, left and ground.

 

[dudio]

Most likely red is right and white is left. It's questionable if yellow is ground since that is an odd colour choice. If there is a bare silver or copper wire, that would most likely be your ground and your Aux plug includes a third conductor likely using yellow for a mic or something.
Your best bet is to use a multimeter and check continuity from each pole on the plug to each wire. A Google search will show you which section of the plug is for right/left/ground etc.