i guess you have been busy enjoying your xmas vacation. how is your fm multiplex project coming along. have not heard a peep from you end about that.
IFTs are assigned different color codes because each color has its own use.
red can - its is the local oscillator coil and it is part of the tuner section composing of the antenna, tuning cap and the mixer/converter transistor. briefly this red can is used to produce a high frequency signal which we call the local oscillator signal.
yellow can - it is an intermediate frequency transfo and the windings are tighly coupled wherein strong signal from the primary winding is coupled to the secondary with a high bandwidth. but selectivity here is poor but it is corrected by the next stage, the white IFT
white can- this IFT is critically coupled wherein the coupling of signal is strenghtened so interference is prevented. however the signal bandwidth is suppressed which in effect degrades the sound quality.
black can - same as white
it is the combination of functions of the yellow and white or black IFTs that improves bandwidth, selectivity and signal strenght to come out with strong clean sound.
i hope you are able to comprehend what am saying here